The Dunedin Study - DMHDRU

Publications

All peer reviewed publications are listed below.

Displaying page 9 of 21.

Thomson, W.M. | 2001
Use of dental services by 26-year-old New Zealanders

New Zealand Dental Journal, 2001, 97(97), 44-48.
Our ref: NZ80

Show abstract » The use of dental services and its oral health associations were investigated in a birth cohort of 26-year-olds in order to examine the oral health and health-care effects of the change in entitlement to State assistance for dental care which occurs once New Zealanders turn 18. Fewer than half were routine users, and this proportion was greater among females. More of those who were episodic users at age 26 rated their oral health poorly, and more than one in six had had a tooth extracted since age 18 because of caries. Those who used dental services only when they had a problem not only had greater caries experience by the age of 26, but their caries increment over the previous eight years was also greater. Visiting the dentist for routine check-ups has better long-term oral health consequences than only going when there is a problem.
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McGee, R., Williams, S.M., Nada-Raja, S. | 2001
Low self-esteem and hopelessness in childhood and suicidal ideation in early adulthood

Journal of Abnormal Child Psychology, 2001, 29(29), 281-291.
Our ref: RO409

Show abstract » This study examined the longitudinal relationship between family characteristics in early childhood, self-esteem, hopelessness and thoughts of self-harm in the midchildhood years, and suicidal ideation at ages 18 and 21. Path analysis was used to establish separate models for boys and girls. The results suggested different pathways to later suicidal ideation for boys and girls. For boys, suicidal ideation seemed to have stronger roots in childhood, with significant paths from low self-esteem and hopelessness to early thoughts of self-harm and thence to later ideation. For girls, self-esteem had a small but significant direct effect on later suicidal ideation. The findings provide support for the idea that individual characteristics such as feelings of hopelessness and low self-esteem act as generative mechanisms, linking early childhood family characteristics to suicidal ideation in early adulthood.
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Begg, D.J., Langley, J.D. | 2001
Changes in risky driving behaviour from age 21 to 26 years

Journal of Safety Research, 2001, 32(32), 491-499.
Our ref: RO408

Show abstract » The aim of this study was to determine whether the prevalence of risky driving behaviour changed between the ages 21 and 26 years, among a cohort of young people. Method: This study was part of the Dunedin Multidisciplinary Health and Development Study, which is a longitudinal study of a birth cohort. This study involved examining changes in the prevalence of risky driving behaviour among young adults at ages 21 and 26 years. At both ages, 936 members of the cohort were administered face-to-face interviews, using a structured questionnaire that included items on a range of risky driving and thrill seeking activities. Results: The results showed that risky driving was a predominantly a male activity, but by 26 years of age many had matured out of this behaviour. At the same time, the desire for thrill-seeking increased among the males. Among the females, there were few significant changes between ages 21 and 26 years but at both ages the prevalence of risky driving and thrill-seeking was relatively low. Impact on industry: These results show that the main target population for road safety interventions aimed at reducing risky driving behaviour should be young, male drivers
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Roberts, B.W., Caspi, A., Moffitt, T.E. | 2001
The kids are alright: Growth and stability in personality development from adolescence to adulthood

Journal of Personality and Social Psychology, 2001, 81(81), 670-683.
Our ref: RO402

Show abstract » This longitudinal study provides a comprehensive analysis of continuity and change in personality functioning from age 18 to age 26 in a birth cohort (N = 921) using the Multidimensional Personality Questionnaire (A. Tellegen, 1982). Data were analyzed using 4 different methods: differential continuity, mean-level change, individual differences in change, and ipsative change. Convergent evidence pointing toward personality continuity, as opposed to change, was found. The personality changes that did take place from adolescence to adulthood reflected growth in the direction of greater maturity; many adolescents became more controlled and socially more confident and less angry and alienated. Consistent with this, greater initial levels of maturity were associated with less personality change over time. The results indicate that the transition from adolescence to young adulthood is marked by continuity of personality and growth toward greater maturity.
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Roberts, B.W., Caspi, A. | 2001
Personality development and the person-situation debate: It's deja vu all over again. Authors' Response.

Psychological Inquiry, 2001, 12(12), 104-109.
Our ref: RO401

Show abstract » Response to commentaries to target article (RO400).
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Caspi, A., Roberts, B.W. | 2001
Personality development across the life course: The argument for change and continuity. Target Article.

Psychological Inquiry, 2001, 12(12), 49-66.
Our ref: RO400

Show abstract » In this article the authors review answers to 5 questions concerning the development of personality across the life course: How early in the life course can we identify characteristics unique to individuals that will show continuity over time? When in the life course is personality fully developed? What life course factors moderate continuity and change in personality? What are the mechanisms that promote continuity in personality? And finally, what are the mechanisms that promote change in personality? Based on the answers to these 5 questions they conclude (a) that there is modest continuity from childhood to adulthood, (b) that personality traits do not become fixed at a certain age in adulthood and retain the possibility of change even into old age, and (c) that with time and age people become more adept at interacting with their environment such that personality consistency increases with age and is more common than change in midlife and old age.
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Locker, D., Poulton, R., Thomson, W.M. | 2001
Psychological disorders and dental anxiety in a young adult population

Community Dentistry and Oral Epidemiology, 2001, 29(29), 456-463.
Our ref: RO395

Show abstract » Objectives. It has been suggested that some individuals who are fearful or anxious about dental treatment have a constitutional vulnerability to anxiety disorders as evidenced by the presence of multiple fears, generalized anxiety or panic disorders. This paper compares the prevalence of psychological disorders among dentally anxious and non-anxious groups drawn from the general population. Methods: Data were obtained as part of a birth cohort study when study members were aged 18 years. They were assessed using the Dental Anxiety Scale (DAS) and the Diagnostic Interview Schedule (DIS). The disorders diagnosed by the DIS were major depressive episode, dysthymia, generalized anxiety disorder, panic disorder, agoraphobia, social phobia, simple phobia, obsessive compulsive disorder, conduct disorder, cannabis and alcohol dependence. Results: Overall, 12.5% of study members had DAS scores of 13 or more and were considered to be dentally anxious. Those who were dentally anxious were more likely than the non-anxious to be diagnosed with one or more psychological disorders (55.0% vs. 42.3%). However, those with DAS scores of 13 or 14 (moderately dentally anxious) were broadly similar to the non-anxious in terms of their psychological profile. This excess prevalence of psychological disorder was largely accounted for by high rates of disorder among those with DAS scores of 15 or more (highly dentally anxious). The highly anxious were more likely than the non-anxious to have a diagnosis of conduct disorder, agoraphobia, social phobia, simple phobia or alcohol dependence. Odds ratios ranged from 2.8 to 5.0 after controlling for the effects of gender. The data also suggested that dentally anxious individuals with psychological disorders were more likely to maintain their anxiety over time. Conclusions: In this population of young adults, high rates of psychological disorder were characteristic of those with high levels of dental anxiety. Psychological disorder was related to the maintenance of dental anxiety over time.
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Belsky, J., Jaffee, S.R., Hsieh, K.H., Silva, P.A. | 2001
Childrearing antecedents of intergenerational relations in young adulthood: A prospective study

Developmental Psychology, 2001, 37(37), 801-813.
Our ref: RO394

Show abstract » Data gathered from mothers on parenting and family climate when almost 1,000 children in the Dunedin, New Zealand, longitudinal study were 3, 5, 7, 9, 13, and 15 years of age were used to predict intergenerational relations between young adult children (age 26) and their middle-aged parents. Analyses focused on distinct developmental epochs revealed greater prediction from the middle-childhood and early-adolescent periods than from the early-childhood years; most indicated that more supportive family environments and child-rearing experiences in the family of origin forecasted more positive and less negative parent-child relationships (in terms of contact, closeness, conflict, reciprocal assistance) in young adulthood, though associations were modest in magnitude. Some evidence indicated that (modestly) deleterious effects on intergenerational relations of experiencing relatively unsupportive child-rearing environments in 1 but not 2 (of 3) developmental periods studied could be offset by relatively supportive family environments in the remaining developmental periods.
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Moffitt, T.E., Robins, R.W., Caspi, A. | 2001
A couples analysis of partner abuse with implications for abuse prevention

Criminology & Public Policy, 2001, 1(1), 5-26.
Our ref: RO393

Show abstract » This research used a couples analysis to test five models of partner abuse: (1) perpetrators' characteristics predict their abusive behavior, (2) victims' characteristics predict their victimization, (3) a dyadic process model in which both partners' characteristics independently and jointly predict couples' reciprocal abuse, (4) a traditional model in which men's characteristics alone predict both men's abuse and women's defensive reactions to it, and (5) an interactive model in which one partner's characteristics can moderate the other partner's abuse risk. We studied a representative sample of 360 young-adult couples comprising non-abusive couples, non-clinical abusive couples, and clinical abusive couples. As outcomes, we used measures of abuse perpetration, and as predictors we used partners' scores on negative emotionality, an indicator of violence-prone cognitions and emotions. Results were consistent with models 1, 2, and 3 for both males and females, but not with models 4 or 5. Findings applied to both non-clinical and clinical abusive couples. This study is the first to identify clinical abusive couples without selection bias (9% of the sample, having injury and/or official agency intervention), and to find that in such couples both sexes engage in abuse. Implications for primary prevention are that prevention programs should aim to: (a) target violence-prone cognitions and emotions, (b) reduce abusive behavior by both sexes, and (c) promote victim safety among both sexes. Implications for rehabilitation of already-abusive couples are: (d) treating only men will not reduce risk completely for most couples, and (e) more resources should be invested in researching couples treatments to reduce abuse. If replicated, the findings would suggest the need for policy that encourages development and evaluation of programs to reduce physical abuse by women.
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Thomson, W.M., Edwards, S.J., Dobson-Le, D., Tompkins, G.R., Knight, D.A., Poulton, R., Braithwaite, A. | 2001
IL-1 Genotype and adult periodontitis among young New Zealanders

Journal of Dental Research, 2001, 80(80), 1700-1703.
Our ref: RO392

Show abstract » Several recent studies have investigated the association between interleukin-1 genotype and periodontitis in clinical samples, where generalizability is an issue. The aim of this study was to investigate the association between adult periodontitis and IL-1 genotype in a population-based sample of 26-year-olds. Based on probing depth (PD) measurements, participants were divided into three disease groups: Severe (1+ teeth with 5+mm PD; N = 25), Moderate (2+ teeth with 4+mm PD; N = 36), and Controls (the remain-der; N = 800). The periodontitis-associated genotype (PAG; Kornman et al., 1997) was present in 20.0% of the Severe group and in 34.8% of Controls, whereas the IL-1A+4845 [1,1]/IL-1B+3953 [2,2] genotype was present in 12.0% and 0.9%, respectively. After controlling for sex, smoking status, and plaque levels, we found that those with IL-1B+3953 [1,1]/IL-1A+4845 [2,2] had 12.3 times the odds of being in the Severe group. Analysis of these data suggests that the IL-1A+4845 [1,1]/IL-1B+3953 [2,2] genotype is associated with periodontal disease in this young population. Future periodontal data collections as this cohort ages are required to confirm the predictive value of that genotype.
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Pisecco, S., Swank, P., Wristers, K., Silva, P.A., Baker, D.B. | 2001
The effect of academic self-concept on ADHD and antisocial behaviors in early adolescence

Journal of Learning Disabilities, 2001, 34(34), 450-461.
Our ref: RO391

Show abstract » Using structural equation modeling techniques, we evaluated the effect of academic self-concept (ASC) on the development of attention-deficit/hyperactivity disorder (ADHD) and antisocial behaviors in early adolescence. Participants (n = 445) were recruited from the Dunedin Multidisciplinary Health and development Research study. Eligibility was determined by the presence of complete data for the following variables at the specified time periods: reading at age 7, teacher reports of ADHD and antisocial behaviors at age 7, self-ratings of ASC at ages 9 and 11, and teacher reports of ADHD and antisocial behaviors at age 13. The results indicated that ASC is an important construct that directly contributes to the development of antisocial behaviors rather than to symptoms of ADHD. The results also indicated that children's, early history of behavioral problems and academic performance contribute to the development of a more robust understanding of the impact of ASC on the development of disruptive behaviors in early adolescence.
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Jaffee, S. R. , Caspi, A. , Moffitt, T. E. , Taylor, A. , Dickson, N. | 2001
Predicting early fatherhood and whether young fathers live with their children: prospective findings and policy reconsiderations

Journal of Child Psychology and Psychiatry, 2001, 42(42), 803-815.
www.ncbi.nlm.nih.gov/pubmed/11583253
Our ref: RO390

Show abstract » This prospective study of a birth cohort addressed three questions. Which individual and family-of-origin characteristics predict the age at which young men make the transition to fatherhood? Do these same characteristics predict how long young men live with their child? Are individual differences in the amount of time fathers spend living with their child associated with the father's psychosocial characteristics in young adulthood? In this unique study, it was found that by age 26, 19% of the 499 study men had become fathers. Individual and family-of- origin characteristics were assessed from birth until age 15 and contemporaneous characteristics were assessed at age 26. Young men who experienced a stressful rearing environment and a history of conduct problems were more likely to become fathers at an early age and to spend less time living with their child. Of those who experienced none of the risk factors, fewer than 10% had become fathers by age 26 compared to more than 60% of those who experienced five risk factors. Fathers who lived apart from their child reported the most social and psychological difficulties in young adulthood. These findings point to individual and family-of-origin characteristics that might be targeted in order to delay fatherhood and increase levels of paternal involvement. However, given their troubled life histories and poor social-psychological adjustment in young adulthood, some absent fathers might have difficulties providing positive parenting and partnering unless policy initiatives to promote intact families also support young fathers.
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Kruger, E., Thomson, W.M., Konthasinghe, P. | 2001
Third molar outcomes from age 18 to 26: Findings from a population-based New Zealand longitudinal study

Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontics, 2001, 92(92), 150-155.
Our ref: RO389

Show abstract » OBJECTIVE: The purpose of this study was to describe the presence and impaction status of people's third molars at age 18 years, as well as the observed changes in their clinical status between ages 18 and 26 years. Study Design: Eight hundred twenty-one participants in a prospective cohort study were dentally examined at ages 18 and 26 years, and panoramic radiographs were taken at age 18 years but not at 26 years. For each tooth, its radiographic impaction status at age 18 years was compared with the clinical status by age 26 years. RESULTS: Of the 2857 third molars assessed at age 18 years, 92.8% were able to be followed up clinically at age 26 years. Approximately 54.9% of the teeth that were not impacted by age 18 had erupted by 26 years. Of the teeth that were impacted by age 18, 33.7% had fully erupted by age 26, 31.4% had been extracted, and 13.1% remained unerupted. Of the maxillary teeth that were categorized as impacted at age 18 years, 36.2% had fully erupted by age 26, whereas only 25.6% of the mandibular teeth had done so (P <.01). Fewer mandibular teeth than maxillary teeth remained unerupted by the time the patient was 26 years old (27.4% and 41.4%, respectively; P <.01), but there was no significant difference between the jaws in the proportion of impacted teeth at age 18 years that had been extracted by age 26 years (29.6% and 30.3%, respectively). For mesioangularly impacted third molars, 39.3% of maxillary teeth and 20.4% of mandibular teeth had fully erupted by age 26. Of the third molars that were mesioangularly impacted at age 18 years, 39.3% of maxillary teeth and 20.4% of mandibular teeth had fully erupted by age 26 years, whereas almost one-third of each had been extracted. Of the distoangularly impacted third molars, 20.4% of the maxillary teeth and one-third of the mandibular teeth had erupted by age 26, with 21.6% of the maxillary teeth and 31.6% of the mandibular teeth having been extracted. CONCLUSION: Other than horizontally impacted third molars, a substantial proportion of other impaction types do erupt fully, and radiographically apparent impaction in late adolescence should not be sufficient grounds for their prophylactic removal in the absence of other clinical indications.
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Eberhart-Phillips, J., Dickson, N. , Paul, C. , Herbison, G. P. , Taylor, J. , Cunningham, A. L. | 2001
Rising incidence and prevalence of herpes simplex type 2 infection in a cohort of 26 year old New Zealanders

Sexually Transmitted Infections, 2001, 77(77), 353-357.
www.ncbi.nlm.nih.gov/pubmed/11588282
Our ref: RO388

Show abstract » OBJECTIVES: To examine changes in the incidence and prevalence of herpes simplex type 2 (HSV-2) infection in a birth cohort of 26 year old New Zealanders in whom seroprevalence had been measured at 3.4% at age 21. METHODS: Sera from 869 cohort members were tested using an indirect IgG enzyme linked immunoassay specific to the HSV-2 glycoprotein G. Serological results were compared with detailed sexual histories. RESULTS: In all, 96 participants (11%) were seropositive for HSV-2, including at least 56 who seroconverted after their 21st birthday. Among those known to be seronegative at age 21, the annual seroconversion rate was 13.5 cases per 1000 per year, compared with 8.1 cases per 1000 per sexually active year before age 21. New infections were associated with female sex and an early age of first intercourse. The average rate of partner change was lower in the cohort after age 21, and was only modestly increased among those who acquired new HSV-2 infections between ages 21 and 26. CONCLUSIONS: HSV-2 seroprevalence has risen sharply in this sexually active cohort, despite a reduction in the overall level of partner change. Increased rates of HSV-2 acquisition after age 21 may be due to a higher prevalence of infection in the pool of potential partners encountered during the third decade of life. Factors related to partner choice may have more influence on the risk of HSV-2 infection than the number of sexual partners alone.
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Poulton, R., Milne, B.J., Craske, M.G., Menzies, R.G. | 2001
A longitudinal study of the etiology of separation anxiety

Behaviour Research and Therapy, 2001, 39(39), 1395-1410.
Our ref: RO387

Show abstract » A longitudinal examination of the relation between separation experiences and the development of separation anxiety at age 3, 11 and 18 years was conducted. Three associative pathways (Rachman, 1977) were assessed. Conditioning events were not related to separation anxiety at age 3. Vicarious learning (modelling) in middle childhood (age 9 years) was the conditioning variable most strongly related to separation anxiety at age 11, accounting for 1.8% of the variance in symptoms. Separation experiences (hospitalisations) before the age of 9 were inversely correlated with separation anxiety at age 18. That is, more overnight hospital stays in childhood were related to less separation anxiety in late adolescence. However, none of these conditioning correlates remained significant predictors of separation anxiety in adjusted regression models. In contrast, certain planned separations in early-mid childhood were associated with lower levels of separation anxiety at later ages. Generally, the findings were consistent with predictions from the non-associative theory of fear acquisition. That vicarious learning processes appeared to modulate, albeit to a minor degree, the expression of separation anxiety during mid-late childhood suggests that there may be critical periods during which some individuals are susceptible to the interactive effects of both associative and non-associative processes. These findings serve to illustrate the complexity of fear acquisition, the relevance of developmental factors and the likely interplay between associative and non-associative processes in the etiology of fear and anxiety.
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Wright, B.R., Caspi, A., Moffitt, T.E., Silva, P.A. | 2001
The effects of social ties on crime vary by criminal propensity: A life-course model of interdependence

Criminology, 2001, 39(39), 321-351.
Our ref: RO386

Show abstract » Previous studies have explained the transition from criminal propensity in youth to criminal behavior in adulthood with several hypotheses: (1) enduring criminal propensity, (2) unique social causation, and (3) cumulative social disadvantage. In this article we develop an additional hypothesis derived from the life-course concept of interdependence: (4) that the effect of social ties on crime vary as a function of individuals' levels of criminal propensity. Prosocial ties, such as ties to education , should deter criminal behavior most strongly among individuals prone to crime. We term this a social-protection effect. Antisocial ties, such as delinquent peers, should promote criminal behavior most strongly among the same, criminally-prone individuals - a social-amplification effect. We tested these four hypotheses with data from the Dunedin Study. In support of previous hypotheses, low self-control predicted more criminal behavior, prosocial ties predicted less crime, and low self-control predicted weaker social ties that led to more crime. In support of life-course interdependence, low self-control significantly interacted with social ties. Prosocial ties, such as education, employment, family ties, and partnerships deterred crime, and antisocial ties, such as delinquent peers, promoted crime, most strongly among individuals displaying low self-control. Our findings bear upon the generalizability of standard psychological and sociological theories of crime and on practical intervention for youthful offenders.
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Locker, D., Thomson, W.M., Poulton, R. | 2001
Psychological disorder, conditioning experiences and the onset of dental anxiety in early adulthood

Journal of Dental Research, 2001, 80(80), 1588-1592.
Our ref: RO385

Show abstract » Most studies examining the origins of dental fear and anxiety have relied on cross-sectional data. These are subject to several problems, such as recall and uncertainty concerning temporal relationships. This paper uses longitudinal data from the Dunedin Multidisciplinary Health and Development Study to assess risk factors for the development of dental anxiety in persons between the ages of 18 and 26 years. It was hypothesized that psychological factors would be as important as conditioning experiences in the genesis of dental anxiety over this period. The eight-year incidence of dental anxiety was 16.5%. Five variables entered models predicting onset: multiple fears, symptoms of substance dependence, previous experience of invasive dental treatment, dental visiting pattern, and the extraction of one or more teeth. Separate analyses for those avoiding and those using dental services resulted in different explanatory models. These results indicated that both psychological and conditioning variables contributed to the development of dental anxiety in this population of young adults.
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Bennett, K. E. , Haggard, M. P. , Silva, P. A. , Stewart, I. A. | 2001
Behaviour and developmental effects of otitis media with effusion into the teens

Archives of Disease in Childhood, 2001, 85(85), 91-95.
www.ncbi.nlm.nih.gov/pubmed/11466180
Our ref: RO384

Show abstract » OBJECTIVE: To examine whether behavioural or cognitive sequelae of otitis media with effusion (OME) continue into late childhood and the early teens (11-18 years). SETTING: Data from a large multipurpose birth cohort study: the Dunedin multidisciplinary health and development study. PARTICIPANTS: Around 1000 children from the study. The main independent variable of interest was otological status of the child up to age 9. MAIN OUTCOME MEASURES: Parent and teacher rated behaviour problems, including antisocial, neurotic, hyperactive, and inattentive behaviours, and tests of academic achievement including intelligence quotient (IQ), reading, and spelling were available in a high proportion of the cohort at ages 11 to 18 years. RESULTS: After adjustments for covariates such as socioeconomic status, hyperactive and inattentive behaviour problems were evident as late as 15 years, and lower IQ associated with OME remained significant to 13 years. The largest effects were observed for deficits in reading ability between 11 and 18 years. CONCLUSIONS: No previous study considering behaviour problems as an outcome has followed children long enough to determine whether some of the early sequelae of OME are still present in the early to late teens. Some developmental sequelae of OME, particularly deficits in reading ability, can persist into late childhood and the early teens.
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Meldrum, A.M., Thomson, W.M., Drummond, B.K., Sears, M.R. | 2001
Is asthma a risk factor for dental caries? Findings from a cohort study

Caries Research, 2001, 35(35), 235-239.
Our ref: RO383

Show abstract » It has been suggested that asthmatic children may have a higher caries risk, both as a result of their medical condition, and the physical and physiological effects of their pharmacotherapy. By examining the association over time between asthma and caries increment, this study tested the hypothesis that childhood asthma is associated with an increased caries increment. In a longstanding New Zealand cohort study, participants long-term asthma histories and the three-year net caries increment between ages 15 and 18 years were examined. Of the 781 who were examined at 15 and 18, 39 participants were consistently taking anti-asthma medication at ages 9, 11, 13 and 15 years (and labelled in this study as medication-determined asthmatics, or MDA); 56 were identified as consistent wheezers at ages 9, 11, 13 and 15 years (wheeze-determined asthmatics, or WDA); and 36 were members of both groups. A smaller group (N=9) were identified as being very long-term asthmatics (asthma at 5 years of age and at ages 9, 11, 13 and 15 years). Some 206 study members were identified as having no history of asthma, asthma medication or significant wheeze at any time up to and including 18 years. The overall mean net caries increment between ages 15 and 18 years was 2.06 surfaces (sd, 3.76). There were no significant differences in caries increment between the 206 asthma-free participants and any of the asthma groups. This study provides little evidence for an asthma-caries causative relationship.
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Locker, D., Thomson, W.M., Poulton, R. | 2001
Onset of and patterns of change in dental anxiety in adolescence and early adulthood: A birth cohort study

Community Dental Health, 2001, 18(18), 99-104.
Our ref: RO382

Show abstract » Objective: To assess the onset of and patterns of change in dental anxiety during adolescence and early adulthood. Design: A birth cohort study of 1,037 individuals born in Queen Mary Hospital, Dunedin, New Zealand between 1 April 1972 and 31 March 1973. Data were collected from these individuals at birth, every two years between the ages of 3 and 15 and at 18, 21and 26 years. Study members Data on dental anxiety were obtained at the 15, 18 and 26-year assessments from 678 study members. Outcomes: Dental anxiety was assessed using the Dental Anxiety Scale. Study members with a score of 13 or over were classified as being dentally anxious. Results: The prevalence of dental anxiety increased from 10.6% at age 15 years to 13.3% at 18 years and 21.1% at 26 years. Of the 31.2% who were anxious at one or more data collection periods, approximately one third were anxious by the age of 15, one third became anxious between 16 and 18 years and one third between 18 and 16 years. High rates of remission were observed. Of 72 study members who were dentally anxious at 15 years, 22% were persistent cases, anxious at all three data collection points; 24% were recurrent cases, anxious at 26 but not anxious at 18 years: and 54% were remitted cases, no longer anxious at 26 years. There were no gender differences in the onset and course of dental anxiety over the developmental periods observed. Conclusions: The period of observation was one of instability with respect to anxiety about dental treatment. Early adulthood in particular appeared to be a life stage during which this population was vulnerable to the onset of dental anxiety. This may be related to dental disease and treatment factors, or changing psychological states during significant life transitions.
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Feehan, M. , Nada-Raja, S. , Martin, J. , Langley, J. D. | 2001
The prevalence and correlates of psychological distress following physical and sexual assault in a young adult cohort

Violence and Victims, 2001, 16(16), 49-63.
Our ref: RO381

Show abstract » Among a birth cohort of New Zealand's 21-year-olds, 41% experienced physical or sexual assault in the previous 12 months. The level of psychological distress experienced by the 374 victims was determined in interviews assessing for symptoms indicative of posttraumatic stress disorder and ratings of impairment in activities of daily living. Of the 141 women victims, 32.6% were identified as experiencing psychological distress as were 9.9% of the 233 men. For men, bivariate analyses showed psychological distress was significantly associated with factors indicative of increased assault severity, and for women an increased likelihood of distress was associated with the location of assault and the relationship to the assailant. Positive indicators of social support were not significantly associated with less adverse psychological outcomes. However, for both men and women, resisting the assailant was associated with a reduced likelihood of psychological distress. Multivariate analyses revealed that for both women and men, unemployment uniquely predicted variance in distress, over and above that accounted for by characteristics of the assault.
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Craske, M.G., Poulton, R., Tsao, J.C.I., Plotkin, D. | 2001
Paths to panic disorder/agoraphobia: An exploratory analysis from age 3 to 21 in an unselected birth cohort

Journal of the American Academy of Child and Adolescent Psychiatry, 2001, 40(40), 556-563.
Our ref: RO380

Show abstract » Objective: To evaluate childhood temperamental traits and early illness experiences in the etiology of adult panic disorder with agoraphobia. Method: Evaluated temperamental and illness experience factors, at ages 3 through 18, as predictors of panic and agoraphobia at ages 18 or 21 in an unselected sample (N = 992). Analyses were conducted with classification trees. Results: Experience with respiratory ill health predicted panic/agoraphobia relative to other anxiety disorders and healthy controls. Also, temperamental emotional reactivity at age 3 predicted panic/agoraphobia in males but did not predict other anxiety disorders, compared with healthy controls. Furthermore, temperament and ill health interacted with gender. Conclusions: Results are discussed in terms of cognitive theories of fear of physical symptoms and biological models of respiratory disturbance for panic/agoraphobia.
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Jaffee, S.R., Caspi, A., Moffitt, T.E., Belsky, J., Silva, P.A. | 2001
Why are children born to teen mothers at risk for adverse outcomes in young adulthood? Results from a 20-year longitudinal study

Development and Psychopathology, 2001, 13(13), 377-397.
Our ref: RO379

Show abstract » This 20-year longitudinal study showed that the young adult offspring of teen mothers are at risk for a range of adverse outcomes including early school leaving, unemployment, early parenthood, and violent offending. We tested how much the effect of teen childbearing on offspring outcomes could be accounted for by social selection (in which a womans characteristics that make her an inadequate parent also make her likely to bear children in her teens) versus social influence (in which the consequences of becoming a teen mother also bring harm to her children, apart from any characteristics of her own). The results provided support for both mechanisms. Across outcomes, maternal characteristics and family circumstances together accounted for approximately 39% of the effect of teen childbearing on offspring outcomes. Consistent with a social-selection hypothesis, maternal characteristics accounted for approximately 18% of the effect of teen childbearing on offspring outcomes and consistent with a social-influence hypothesis, family circumstances accounted for 21% of the teen childbearing effect after controlling for maternal characteristics. These results suggest that public policy initiatives should be targeted not only at delaying childbearing in the population, but at supporting individual at-risk mothers and their children.
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Moffitt, T.E., Caspi, A. | 2001
Childhood predictors differentiate life-course persistent and adolescence-limited antisocial pathways among males and females

Development and Psychopathology, 2001, 13(13), 355-375.
Our ref: RO378

Show abstract » This article reports a comparison on childhood risk factors of males and females exhibiting childhood-onset and adolescent-onset antisocial behavior, using data from the Dunedin longitudinal study. Childhood-onset delinquents had childhoods of inadequate parenting, neurocognitive problems, and temperament and behavior problems, whereas adolescent-onset delinquents did not have these pathological backgrounds. Sex comparisons showed a male to female ratio of 10:1 for childhood-onset, but a sex ratio of only 1.5:1 for adolescence-onset delinquency. Showing the same pattern as males, childhood-onset females had high-risk backgrounds, but adolescent-onset females did not. These findings are consistent with core predictions from the taxonomic theory of life-course persistent and adolescence-limited antisocial behavior.
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Poulton, R., Waldie, K.E., Thomson, W.M., Locker, D. | 2001
Determinants of early- versus late-onset dental fear in a longitudinal epidemiological study

Behaviour Research and Therapy, 2001, 39(39), 777-785.
Our ref: RO377

Show abstract » A longitudinal investigation of risk factors for Early- and Late-onset dental fear was conducted. Early-onset dental fear was related to conditioning experiences (indexed via caries level and tooth loss), service use patterns, stress reactive personality and specific beliefs about health professionals. Late-onset dental fear was related to aversive conditioning experiences, irregular service use and an external locus of control. In contrast to recent findings for dental anxiety, personality factors were not strongly related to the onset of dental fear in young adulthood. The key role played by conditioning events in the development of both Early- and Late-onset dental fear was confirmed. Conditioning events appear to play a different role in the development of dental fear versus dental anxiety. This may reflect important, but largely ignored differences between these two closely related constructs. Interventions for Early-onset dental fear should aim to modify both the dental fear and the personality vulnerabilities that may contribute to the development of dental fear early in the life-course.
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Talley, N. J., Howell, S., Poulton, R. | 2001
The irritable bowel syndrome and psychiatric disorders in the community: Is there a link?

American Journal of Gastroenterology, 2001, 96(96), 1072-1079.
Our ref: RO376

Show abstract » OBJECTIVE: Psychiatric morbidity is high among patients who present to referral centers with irritable bowel syndrome (IBS). However, few studies have investigated the relationship between psychiatric disturbance and IBS in community samples. We hypothesized that psychiatric disorders are linked to IBS in the general community, but this is influenced by the criteria used to establish a diagnosis of IBS. METHODS: The data were collected from a birth cohort born in Dunedin (New Zealand) between April 1972 and March 1973. This cohort consisted of 1037 members (52% male), who were assessed at ages 3, 5, 7, 9, 11, 13, 15, 18, 21, and 26 yr. GI symptoms were recorded at age 26 yr, using an abbreviated version of the Bowel Symptom Questionnaire; psychiatric history was obtained at ages 18 and 21 yr, using a modified version of the Diagnostic Interview Schedule. RESULTS: The prevalence of IBS was 12.7% according to the Manning criteria and 4.3% according to the Rome II criteria. The IBS was not significantly related to a diagnostic history for psychiatric illness overall. nor to a history of anxiety disorders, depressive disorders, and substance dependence. These results were independent of the IBS criteria used, there was no association between psychiatric history and IBS when IBS was defined according to the Manning criteria (p = 0.11 to 0.98) or the Rome criteria (p = 0.18 to 0.92): Rome and Manning criteria subjects did not significantly differ from each other in terms of psychiatric history (p = 0.16 to 0.89). CONCLUSION: In a cohort of young adults with IBS from New Zealand, IBS appears to not be related to psychiatric disorders.
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Pisecco, S., Baker, D.B., Silva, P.A., Brooke, M. | 2001
Boys with reading disabilities and/or ADHD: Distinctions in Early Childhood

Journal of Learning Disabilities, 2001, 34(34), 98-106.
Our ref: RO375

Show abstract » Examined distinctions in the early childhood characteristics of boys with reading disabilities and/or ADHD. A four group mixed design consisting of boys identified at age 11 with reading disabilities only (RD only; N=46), reading disabilities and ADHD (RD/ADHD; N=16), ADHD only (N=20), and a comparison group (N=281) was utilized. Differences on receptive and expressive language and temperament for ages 3 and 5, were investigated. Analyses indicated that the boys from the RD only group performed worse on measures of receptive and expressive language. The results also indicated that boys from the RD/ADHD groups consistently performed worse on measures of receptive language and exhibited more behaviors indicative of an under-controlled temperament. In summary we suggest that reading disabilities and ADHD represent moderately unique disorders, which frequently co-occur and are characterized by distinct developmental pathways.
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Hashim, R., Thomson, W.M., Pack, A.R.C. | 2001
Smoking in adolescence as a predictor of early loss of periodontal attachment

Community Dentistry and Oral Epidemiology, 2001, 29(29), 130-135.
Our ref: RO374

Show abstract » Objectives: On the basis of information from studies of older adults, smoking is considered to be an important risk factor for periodontal disease. Examining periodontal loss of attachment among younger adults means a lower contribution from cumulative exposure to other environmental risk factors. The aim of this study was to examine the role of chronic exposure to cigarette smoking as a risk factor for greater prevalence and extent of periodontal loss of attachment among 26-year-old participants in a longstanding prospective cohort study. Methods: Loss of attachment (LOA) was measured at three sites per tooth in two randomly selected contralateral quadrants (one upper, one lower). Cigarette smoking history was obtained at ages 15, 18, 21 and 26, and used to categorise participants as never-smokers, ever-smokers, long-term smokers or very long-term smokers. Results: Periodontal data were available for 914 Study members, among whom 33.6%, and, after controlling for sex, self-care and dental visiting, they were nearly three times as likely to have one or more sites with 4+mm LOA. Conclusions: Chronic exposure to smoking is a strong predictor of periodontal disease prevalence in young adults.
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Williams, S.M. | 2001
Overweight at age 21: the association with body mass index in childhood and adolescence and parents' body mass index. A cohort study of New Zealanders born in 1972-73

International Journal of Obesity, 2001, 25(25), 158-163.
Our ref: RO373

Show abstract » Background: Obesity is an increasing problem so understanding the association between childhood and adolescent measures of body mass index (BMI) and being overweight at age 21 has implications for treatment or strategies to reduce its prevalence. Objective: To examine the association between measures of BMI in childhood and adolescence and parents' BMI and being overweight at age 21. Design: The study was based on a birth cohort born in Dunedin, New Zealand, in 1972-73. Results: BMI tracked from childhood to early adulthood. The point on the BMI distribution where the probability of being overweight at age 21 was 0.5 was close to the 75th centile for boys throughout childhood and adolescence. It was rather higher for girls in childhood but similar in adolescence. Boys with a BMI above the 75th centile at age 7 were more than 4.0 times more likely to be overweight at age 21 than those with a BMI below the median. The relative risk for girls was 3.2. By age 15 this increased to 9.8 for males and 6.8 for females. Having overweight parents, particularly a mother, increased the likelihood of being overweight. Only 40% of those who were overweight at age 21 could be identified by age 7 and 25% were not identified until they were at least 15. Conclusion: Although a high BMI in childhood predicts being overweight at age 21, many of those who were overweight at age 21 had a BMI below the 75th centile or even the median in childhood and early adolescence. Population strategies, complemented by an individual approach for those above the 75th centile, are needed to reduce the average BMI of the population.
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Waldie, K.E. | 2001
Childhood headache, stress in adolescence, and primary headache in young adulthood: A longitudinal cohort study

Headache, 2001, 41(41), 1-10.
Our ref: RO369

Show abstract » Objectives. To determine the association between childhood history of headache, adolescent stress, and headache syndromes (determined by International Headache Society criteria) in young adulthood. Background. The association between stress and tension-type headache has recently been challenged. Little is known about stress and other headache subtypes, particularly among young people from the general population. Design. Members of the longitudinal Dunedin Multidisciplinary Health and Development Study participated in this study. Study members were asked about headache characteristics/symptoms at age 26 (96% of the living cohort) and historical records were examined to ascertain headache history (< 12 yrs) and the reporting of stressful life events at age 15. Results. Study members with childhood headache were significantly more likely to report adolescent stress than those without headache. High intensity stress during mid-adolescence increased the likelihood of migraine diagnosis. In the case of combined headache (individuals with migraine attacks as well as tension-type headache) this relation held only for those with a history of headache. Stress associated with bodily changes during mid-adolescence was the only significant predictor of tension-type headache. Conclusions. Childhood headaches are related to the appraisal of life events reported during mid-adolescence. Childhood headaches also appear to confer a specific risk for the development of combined headache. There was little evidence for a prospective relation between stress in mid-adolescence and tension-type headache in young adulthood, supporting claims that proximal (rather than distal) stress is associated with this disorder.
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Poulton, R., Waldie, K.E., Menzies, R.G., Craske, M.G., Silva, P.A. | 2001
Failure to overcome 'innate' fear: A developmental test of the non-associative model of fear acquisition

Behaviour Research and Therapy, 2001, 39(39), 29-43.
Our ref: RO359

Show abstract » The non-associative, Darwinian theory of fear acquisition proposes that some individuals fail to overcome biologically-relevant fears (e.g. height) because they (1) do not have sufficient safe exposure to the relevant stimuli early in life or (2) are poor habituators who have difficulty learning not to fear. These two hypotheses were tested in a longitudinal birth cohort study. Study 1 found evidence for reduced exposure to height stimuli in childhood for individuals with a fear of heights compared to study members without fear. Study 2 found evidence for higher levels of stress reactivity (a proxy for habituation) in childhood and adolescence among 18-year-old height phobics compared to study members with dental phobia and those with no fear. The results were discussed in relation to recent findings suggesting that some evolutionary-relevant fears may appear in the absence of traumatic learning experiences. The merits of adding a fourth, non-associative pathway to Rachman's [Rachman, S. (1977)] The conditioning theory of fear acquisition: a critical examination (Behavior Research and Therapy, 15, 375-387) three pathways model of fear acquisition were briefly considered.
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Milne, B.J., Waldie, K.E., Poulton, R. | 2000
Users of unconventional practitioners: a profile of 26 year old New Zealanders

New Zealand Medical Journal, 2000, 113(113), 396-399.
Our ref: NZ79

Show abstract » Aims: To profile 26 year old New Zealand unconventional practitioner users. Methods: 977 members of the Dunedin Multidisciplinary Health and Development Study participating in the age-26 assessment (1998-1999) answered questions about 12-month health service use, education, income, recent medical history, current health status and avoidance of medical situations. Results: 10% had used an unconventional practitioner in the previous 12 months. The majority (88%) had also used a conventional practitioner. Those using both types of practitioner were heavy users of health services (12 visits/year). Compared to those who used conventional practitioners exclusively, they had significantly higher incomes and were more likely to report a serious injury, a current disability, a history of back problems, role limitations due to physical health problems, and more bodily pain (all p <0.01). Conclusions: 26 year old New Zealand users of unconventional practitioner have a similar profile to their counterparts in other developed countries. It appears that their health needs are not fully met by conventional services, emphasising the need for more research into the aetiology and treatment of ailments (eg, back pain) for which unconventional practitioners are commonly sought. The Medical Council of New Zealand guidelines on unconventional medicine are discussed in light of these findings.
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Williams, S.M. | 2000
Body Mass Index growth curves for use in New Zealand

New Zealand Medical Journal, 2000, 113(113), 308-311.
Our ref: NZ78

Show abstract » Aim: To construct reference curves for body mass index (BMI) and estimate the prevalence of obesity or being overweight at ages 18 and 21 years. Methods: Smoothed BMI curves were derived from data from a birth cohort born in Dunedin in 1972-73, followed up at two yearly intervals from age three to 15 years, and then at ages 18, 21 and 26 years. Results: Nine curves 0.67 SD apart, corresponding to the 0.4, 2, 9, 25, 50, 75, 91, 98, 99.6 centiles are provided. The prevalence of obesity, a BMI of 30 kg/m or more, was 2.7% for men and 2.6% for women at age 18 years, and 5.8% for men and 5% for women at age 21 years. At age 18 years, 14.9% men and 16.8% of women were overweight, with a BMI between 25 kg/m and 30 kg/m. The prevalence increased to 24.7% for men and 24.2% for women at age 21 years. Conclusion: At age 18 years, the value of the 98th centile was close to WHO criteria defining obesity in adults. This suggests that it could be used to describe obese children and adolescents. The 75th centile could be used in a similar way to delineate those regarded as overweight.
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Allen, T, Thomson, W.M., Emmerton, L.M., Poulton, R. | 2000
Nutritional supplement use among 26-year-olds

New Zealand Medical Journal, 2000, 113(113), 274-277.
Our ref: NZ77

Show abstract » Aims: To estimate the prevalance of use of nutritional supplements among young adults, to examine the source of those supplements and to investigate sex differences in usage. Methods: Participants in the age-26 years assessments of the Dunedin Multidisciplinary Health and Development Study were asked to bring containers for any medication (including supplements) taken in the previous two weeks. Medication data (including prescription source) were recorded and analysed for 978 of 980 Study members. Results: The prevalence of supplement use was 16.6%; 20.4% among females and 13.3% for males (p<0.01). Multivitamin preparations were the most widely consumed, followed by water-soluble vitamin supplements (such as folate and vitamin C). Folate use was higher among females and was taken by 35.7% of pregnant females. Most supplements were self-prescribed, although a doctor had prescribed over one-third of the mineral supplements. Most supplements had been taken for weeks or months, rather than years. Conclusions: Nutritional supplement usage among young adults is reasonably common, and involves a wide range of preparations. The extent of use among younger people suggests a need for regulation of their manufacture, sale and usage, and research to examine their efficacy.
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Begg, D.J., Langley, J.D. | 2000
Seatbelt use and related behaviours among young adults

Journal of Safety Research, 2000, 31(31), 211-220.
Our ref: RO372

Show abstract » Seat belt use among young adults was examined to identify factors associated with non-use. This research was part of the Dunedin Multidisciplinary Health and Development Study which is a study of the health, development and behaviour of a birth cohort of young New Zealanders (n=1037). At age 21 years, 948 (93%) members of this cohort were administered a face-to-face interview where they were asked about seat belt use (own and friends'), reasons for non-use, and also their involvement in risky driving practices, motor vehicle traffic crashes, and some thrill-seeking activities. Results showed relatively high front seat belt use (85-96%) but low rear use (29-47%). Some differences in use were a function of gender and seating location. Generally, users had higher academic qualifications and lower risky driving behaviour (males only), but did not differ significantly as far as crash experiences, and thrill-seeking activity was concerned. The main reasons for not using a seat belt were forgetfulness/laziness, a perceived low risk of injury, and discomfort. This study provided information about the background and behaviour of young adults who do not use seat belts, which could be helpful when designing strategies to promote seat belt use in this age group.
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Krueger, R.F., Caspi, A., Moffitt, T.E. | 2000
Epidemiological personology: The unifying role of personality in population-based research on problem behaviors

Journal of Personality, 2000, 68(68), 967-998.
Our ref: RO371

Show abstract » Epidemiological personology refers to a paradigm in which a developmental perspective on individual differences is paired with a population-based sampling frame to yield insights about the role of personality in consequential social outcomes. We review our work in epidemiological personology, linking personality to diverse, problematic social outcomes: Mental disorders, health-risk behaviors, and violence. We conclude that broad-band personality measurement is both feasible and fruitful in large-scale research on problem behaviors, and we call for increased collaboration between personality psychologists and researchers in fields such as public health, epidemiology, and sociology.
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Thomson, W.M., Locker, D., Poulton, R. | 2000
Incidence of dental anxiety in young adults in relation to dental treatment experience

Community Dentistry and Oral Epidemiology, 2000, 28(28), 289-294.
Our ref: RO370

Show abstract » Objectives: To document the incidence of dental anxiety among individuals aged 18 years at baseline and 26 years at follow-up, and to determine if dental treatment experience continues to play a significant etiological role with respect to the onset of dental anxiety in young adults. Methods: Dental anxiety scale (DAS; Corah, 1969) scores at ages 15, 18 and 26 were obtained for Study members in the Dunedin Multidisciplinary Health and Development Study. Dental examinations were conducted, and sociodemographic and dental service-use data were collected using a self-report questionnaire. Using a case definition of a DAS score of 13 or more, age 18-26 incident cases were identified and their dental treatment experience and service-use characteristics compared with the remainder. Results: DAS scores at 18 and 26 were available for 792 (80.8%) of the 980 26-year- old Study members. An increase in dental anxiety prevalence was observed over the eight-year period, with an annualized incidence of 2.1%. Fewer incident cases had visited a dentist in the previous eight years, and there were no differences between incident cases and others in their eight-year DFS, FS or tooth-loss increments. A subgroup of recurrent cases was identified who were dentally anxious at 15 and 26 but not at 18, and their eight-year incidence of tooth loss due to caries was substantially higher than non-cases. Conclusions: Aversive conditioning experiences appear to be unrelated to the adult onset of dental anxiety, and it may be that particular temperamental or psychological traits are associated with the condition.
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Waldie, K.E., Poulton, R., Kirk, I.J., Silva, P.A. | 2000
The effects of pre- and post-natal sunlight exposure on human growth: evidence from the southern hemisphere

Early Human Development, 2000, 60(60), 35-42.
Our ref: RO368

Show abstract » Several recent studies have reported a causal association between stature and month of birth. Perinatal exposure to sunlight has been suggested as the principal factor underlying this relationship, although the mechanisms involved remain a matter of debate. The longitudinal design of the present study allowed us to directly test the influence of perinatal sunlight exposure (and other meteorological and behavioural factors) on body size at birth and at regular intervals up to age 26. The findings confirmed that prenatal sunlight is one of the most significant determinants of height. However, the trimester of greatest influence differs depending on the age at which study members were measured.
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McGee, R., Williams, S.M. | 2000
Does low self-esteem predict health compromising behaviours among adolescents

Journal of Adolescence, 2000, 23(23), 569-582.
Our ref: RO367

Show abstract » It is often believed that low self-esteem is associated with such health-compromising behaviours in adolescence as substance use, early sexual activity, eating problems and suicidal ideation. Surprisingly, there is little longitudinal research addressing this issue. This longitudinal study examines the predictive association between both global and academic self-esteem from ages 9 to 13 years, and a variety of health compromising behaviours at age 15, in a large sample of young New Zealanders. Levels of global self-esteem significantly predicted adolescent report of problem eating, suicidal ideation, and multiple health compromising behaviours. Earlier levels of self-esteem were unrelated to later substance use and early sexual activity. The findings are discussed in terms of their implications for efforts to raise self-esteem among young people.
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Paul, C., Fitzjohn, J., Herbison, G.P., Dickson, N. | 2000
The determinants of sexual intercourse before age 16

Journal of Adolescent Health, 2000, 27(27), 136-147.
Our ref: RO366

Show abstract » PURPOSE: To identify risk and protective factors for initiation of sexual intercourse before age 16 years at the level of the individual, family, and school. METHODS: A longitudinal study based on a cohort of 1020 people born in Dunedin, New Zealand in 1972/73 and followed up to age 21 years. Demographic characteristics of the sample were similar to the New Zealand population of that age, except that a smaller proportion (3%) were Maori or Pacific Island Polynesian. Information on individual, family and school factors was collected by interview with parents at ages 3, 5, 7 and 9 years and then by postal questionnaire two-yearly up to 15 years. Subjects were assessed two-yearly from age 3 years and interviewed about their behaviours and ambitions at ages 11, 13, and 15 years. Questions about age at first intercourse were asked by computer at age 21 years. Multivariate logistic regression was used to model associations with age of first intercourse less than 16 years. RESULTS: Data on age at first intercourse were available for 926/1020 (91%) of surviving members of the cohort assembled at age 3 years. Overall 27.5% of males and 31.7% of females reported sexual intercourse before age 16 years. In multivariate analyses the independent predictors for early sexual initiation for males were: not having outside home interests at age 13 years, no religious activity at age 11 years, not being attached to school at age 15 years, a low reading score, and a diagnosis of conduct disorder in early adolescence. For females, independent predictors were: socioeconomic status in the middle range, mother having her first child before age 20 years, IQ in the middle range, not being attached to school, being in trouble at school, planning to leave school early, cigarette smoking and higher self-esteem score. CONCLUSIONS: Individual and school factors appear to be more important than family composition or socioeconomic status in the decision to have sexual intercourse before age 16 years. The lowering of age at first intercourse may be partly a cohort effect related to high rates of teenage childbearing in the mothers' generation, and to changes in social acceptability of early sexual behaviour.
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