To predict the severity of mental disease, consider the family

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"There are lots of kids with behavior problems who may outgrow them on their own without medication, versus the minority with mental illnesses that need treatment," said Terrie Moffitt, a professor of psychology and neuroscience in the IGSP. "Family history is the quickest and cheapest way to sort that out."

Researchers who are on the hunt for genes responsible for mental disorders might also take advantage of the discovery, added Avshalom Caspi, an IGSP investigator and professor of psychology and neuroscience. "It suggests they may be better off selecting people with more serious illness or, better still, collecting family history information directly," he said.

That mental illnesses tend to run in families is certainly no surprise. In fact, psychiatric conditions are some of the most heritable of all disorders. But the link between family history and the seriousness of psychiatric disease has been less certain.

Moffitt, Caspi and their colleagues looked to 981 New Zealanders born at a single hospital in 1972 or 1973, who are participants in what is known as the Dunedin Study. Researchers have been tracking the physical and mental health and lifestyles of those enrolled in the longitudinal study since they were 3 years old.

In this case, Caspi and Moffitt's team tested each individual's personal 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. The 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. Contrary to earlier reports, those with a stronger family history did not necessarily develop their disorders at an earlier age.

Family history could be used to identify those in need of early intervention or more aggressive treatment, the researchers said. But if a few, simple questions could have that much value, why has family history been ignored for so long?

Moffitt said that health professionals have shied away from 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 -- that people may not know or may make incorrect assumptions," she said.

The new findings suggest those concerns may be overblown. One key, they say, is in how you go about asking the questions.

For example, instead of asking each person if any of their relatives had a history of anxiety disorder outright, the researchers asked, "Has anyone on the list of family members ever had a sudden spell or attack in which they felt panicked?" If the interviewee came up with a name, they were then asked, "Did this person have several attacks of extreme fear or panic, even though there was nothing to be afraid of?"

There is another very practical reason that those in the mental health profession don't ask about family history. The "bible of psychiatry," officially known as The Diagnostic and Statistical Manual of Mental Disorders (DSM), makes no mention of it. The DSM is the primary tool for making mental health diagnoses and delivering mental healthcare in the U.S. and, to some extent, in other countries around the world.

"There's nothing about family history in the DSM even though it may be the most important," Moffitt said. There will soon be an opening to fix that. Experts including Moffitt are now in the process of revising the DSM, which is currently in its fourth edition. The next edition, DSM-V, is due for publication in 2012.

Duke University