BMJ  2006;333 (22 July), doi:10.1136/bmj.333.7560.0-e

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The children of depressed parents have a persistently high risk of mental illness

Research question What is the long term outlook for people who have at least one parent with major depression?

Answer They have a high risk of mental illness that starts early and continues into early middle age

Why did the authors do the study? It's clear that depression is passed from generation to generation, but we don't know what happens to the children of depressed parents as they grow up and mature. These authors wanted to know the long term outlook for people who have at last one parent with a history of major depression.

What did they do? Twenty years ago, these authors recruited a group of 125 children, teenagers, and young adults with at least one depressed parent. The parents had moderate or severe major depression and were attending psychiatric outpatient clinics. The authors also recruited a similar group of 95 offspring without a depressed parent for comparison. The whole cohort was interviewed and assessed for mental and physical health problems at baseline, then 2 years, 10 years, and 20 years after recruitment. Assessments were done by researchers (who were unaware of each participant's history or their parent's history) using validated instruments such as the schedule for affective disorders and schizophrenia, the global assessment scale, and a checklist of medical illnesses.

The authors have already reported their findings at 10 years, when participants had a mean age of 25 years. Their current study reports findings from the 20 year follow-up, when participants had a mean age of 35 years. Of the original cohort of 220 participants, 151 were interviewed for this study.

What did they find? During the 20 years of the study, the offspring of depressed parents were three times more likely than controls to have major depression (65% v 27%, adjusted relative risk 3.3, 95% CI 2.0 to 5.7), and three times more likely to have an anxiety disorder (67% v 34%, 2.9, 1.6 to 5.1), mostly phobias. They were also more likely to have alcohol and drug dependence, although the difference was not statistically significant (19% v 8%, 2.7, 0.9 to 7.7).

The excess risk of depression started young and remained high throughout the 20 years of follow-up, with a peak age of onset between 15 and 20 years. By the end of the study, 83% of the 101 offspring of depressed parents had had a mental illness, and 65% had been depressed.

Offspring of depressed parents had more outpatient treatment for mental health problems than controls (37/101, 37% v 7/50; 14%, adjusted odds ratio 3.56; 95% CI 1.3 to 10). They also reported more physical illness, particularly cardiovascular disease and neuromuscular problems, and poorer social adjustment.

What does it mean? This study confirms poor mental health associated with having a depressed parent, and suggests that it starts early and continues at least into early middle age. The cohort was fairly small, however, so the findings on specific mental illnesses (such as substance misuse) weren't that robust. The offspring in this study had a parent with moderate or severe depression. The findings may not apply to the children of parents with milder illness who would be treated in primary care.

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Weissman MM et al. Offspring of depressed parents: 20 years later. Am J Psychiatry 2006;163: 1001-8[Abstract/Free Full Text]

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Depression or malign parenting – what is the key antecedent of mental illness in young people?

Woody Caan
bmj.com, 23 Jul 2006 [Full text]