Research Review

Offspring of Parents Psychiatric Illness Have Increased Risk of Developing Mental Disorders

Offspring of two parents with schizophrenia or bipolar disorder appear more likely to develop the same illness or another psychiatric condition than those with only one parent with psychiatric illness, according to a report in the Archives of General Psychiatry.

Reseachers studied a population-based cohort of 2.7 million individuals born in Denmark. They matched records in a general registry of the population with a database of psychiatric admissions. They identified individuals whose parents had both been admitted to psychiatric facilities for schizophrenia and bipolar disorder, and compared the rate of psychiatric admissions for these individuals to those of offspring with one or no parents admitted to psychiatric facilities.

Rates of schizophrenia were highest among offspring of two parents with schizophrenia. Of the 196 couples who both had schizophrenia, 27.3% of their 270 children were admitted to a psychiatric facility, increasing to 39.2% when schizophrenia-related disorders were included. This compared with a rate of 7% among 13,878 offspring of 8,006 couples in which one parent had schizophrenia and 0.86% in 2.2 million offspring of 1 million couples in which neither parent was admitted for schizophrenia.

Similarly, the risk of bipolar disorder was 24.9% in 146 offspring of 83 parent couples who were both admitted for bipolar disorder (increasing to 36% when unipolar depressive disorder was also included). This compared with a risk of 4.4% among 23,152 offspring of 11,995 couples with only one parent ever admitted for bipolar disorder and 0.48% in 2.2 million children of 1 million couples with neither parent ever admitted.

When one parent had bipolar disorder and the other had schizophrenia, offspring had a 15.6% risk of schizophrenia and an 11.7% risk of bipolar disorder.

“It is important to keep in mind that the yields from genetic epidemiology and the strategies implemented are applicable to groups of people, not to the individuals themselves,” they concluded. “However, by joining advances in molecular genetics that are adapted for use in epidemiological genetic screening, our kinds of data with the risk groups described might lead to a large and rapid step forward in the understanding of the etiologies of major mental disorders.”

— Source: American Medical Association