Look to family history to help predict severity of mental disease

Tuesday 7th July 2009

People are routinely asked by doctors about their family history of medical problems such as cancer, diabetes, and heart disease. But up until now, this has not been the case for mental illnesses.

New findings by an international group including University of Otago researchers make a strong case for changing current practice. They report that a short question-and-answer session about a person's relatives and their symptoms of depression, anxiety, or substance abuse is enough to predict not only whether the interviewee is at greater risk for developing each disorder, but also how severe that future illness is likely to be.

The findings come from the Dunedin Multidisciplinary Health and Development Study, which has followed 1000 people born at Queen Mary Hospital in Dunedin in 1972-73 from birth through to age 32. The researchers have been tracking the physical and mental health and lifestyles of study members since they were three years old.

"We already knew that mental illnesses tend to run in families, and are among the most heritable of all disorders," says Professor Richie Poulton, Director of the Dunedin Study and one of the research authors, "what we didn't know was how closely family history was linked to the seriousness of mental illnesses, and that's what this study has helped us find out."

The research team tested each individual's experience with depression, anxiety, alcohol dependence and drug dependence in relation to their family history "scores" – the proportion of their grandparents, parents and siblings over age 10 who were affected. Their analysis shows that family history can predict a more recurrent course of each of the four disorders. It is also indicative of those more likely to suffer a worse impairment and to make greater use of mental health services.

Family history could therefore be used to identify those in need of early intervention or more aggressive treatment for mental illnesses.

For various reasons, however, family histories have not been used in the diagnosis of mental illnesses before now. Professor Terrie Moffitt of the Duke Institute for Genome Sciences and Policy, a co-author of the research, says that health professionals have tended to avoid questioning people about their family history of mental illnesses because of the stigma attached to them.

"There's a sense that families are not as open about mental disorders," Professor Moffitt says.
A second reason is that the "bible" of psychiatry, the Diagnostic and Statistical Manual of Mental Disorders (DSM), makes no mention of family health history. Professor Moffitt and other experts are currently in the process of revising the current version of the DSM, so future editions may well include family health history as an important part of screening for mental illnesses.

Funding for the study came from the New Zealand Health Research Council, US National Institutes of Mental Health, UK Medical Research Council, and the William T Grant Foundation (USA). Coauthors on the study include Barry Milne, Terrie Moffitt, Avshalom Caspi, HonaLee Harrington, and Michael Rutter.

The report appears in the July issue of Archives of General Psychiatry.