Children of Psychiatrically Ill Parents at Risk for Mental Disorders

From Medscape Medical News
Allison Gandey

March 4, 2010 — Children of 2 parents with schizophrenia or bipolar disorder are more likely to develop these or other mental disorders, a new national study shows.

Young people with both parents diagnosed as having schizophrenia were 27% more likely to develop the illness.
The risk of bipolar disorder was similar at almost 25%.

In contrast, people with only 1 parent with a psychiatric illness were much less likely to develop mental disorders. Just 7% of those with a parent with schizophrenia developed the disease.
Only 4% of people with 1 parent with bipolar disorder had the disorder.

The population-based study of 2.7 million people in Denmark is published in the March issue of Archives of General Psychiatry.

Irving Gottesman has been a leader in psychiatric genetic epidemiology for many decades.
"I think we set a world record in terms of the number of parent couples we looked at," lead investigator Irving Gottesman, PhD, from the University of Minnesota Medical School in Minneapolis, said during an interview. "Our cohort included 196 couples with 270 offspring — this is very large," he said.

"Irving Gottesman has been a leader in psychiatric genetic epidemiology for many decades," James Potash, MD, from Johns Hopkins University in Baltimore, Maryland, told Medscape Psychiatry.

"This gigantic study gives us hard numbers to help assess risk," he said.

Large Study

The research team linked data from the Danish civil registration system to the Danish psychiatric central register. Investigators wanted to determine the risk of schizophrenia, bipolar disorder, unipolar depressive disorder, or any diagnosis.

The risk for any psychiatric disorder in offspring with both parents with schizophrenia was close to 68%. For 2 parents with bipolar disorder, the risk was 44%.

During an interview, Dr. Gottesman acknowledged the increased risk, but he also pointed to the high numbers that suggest no diagnosis at all.

"This is something that was cut from the paper because there wasn't enough space to elaborate, but if you do the math and follow the numbers through, you will see high rates with no later diagnosis," he said.

For children with both parents with schizophrenia, the chance of no diagnosis was 73%. For children with both parents with bipolar disorder, the rate was 75%.

"This is good news for many people," Dr. Gottesman said.

Weighing the Risk

Dr. Potash said he agrees that most offspring will not be diagnosed as having mental disorders. "The risk is certainly higher, but many won't become ill." He also points out that this study is consistent with previous work.

"For the practicing clinician," Dr. Gottesman said, "I think this paper speaks to the importance of taking a careful family history."

He notes the many challenges of the intake interview — particularly when it comes to discussing psychiatric health. "People are often embarrassed about mental disorders and keep them secret. Not everyone in a family will necessarily know."

Dr. Gottesman points out that it can be helpful to ask related questions about alcohol and drug use, including more subtle questions about weekly consumption.

Arch Gen Psychiatry. 2010;67:252-257.