Assortative Mating Among Bipolar Patients in the United States Increases Risk for Illness in Offspring

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The presence of unipolar depression in the spouse of someone with bipolar depression was associated with unipolar depression in their offspring, who had a 41.5% risk for developing that disorder.
The presence of unipolar depression in the spouse of someone with bipolar depression was associated with unipolar depression in their offspring, who had a 41.5% risk for developing that disorder.

As reported in an article in the European Archives of Psychiatry and Clinical Neuroscience, individuals with bipolar disorder are more likely to engage in assortative mating in the United States than in Europe, as were their parents before them, thus putting their offspring at greater risk for bipolar disorder, depression, alcoholism, and other psychiatric illnesses.

Robert M. Post, MD, of the Bipolar Collaborative Network, Bethesda, Maryland, and the department of psychiatry and behavioral sciences, George Washington University, Washington, DC, and colleagues recruited 968 outpatients with a diagnosis of bipolar disorder I from 4 cities in the United States and 3 cities in Europe. Participants were asked whether they had children and 477 answered that they had one or more children. A family section of the questionnaire asked about the presence of a diagnosis in the patient's mother and father, spouse, and offspring. Diagnoses included unipolar depression, bipolar disorder, a serious suicide attempt or suicide, alcohol or drug abuse, or other psychiatric illness such as anxiety disorder, panic attacks, eating disorders, attention-deficit disorder, behavioral problems, obsessive compulsive disorder, autism, etc.

Significantly more psychiatric illness was found in the spouses of US participants (31%) than European participants (9%), including unipolar depression, alcoholism, drug abuse, and other illness. Likewise, the offspring of US participants had significantly more psychiatric illness than European participants, with the exception of suicide attempts.

The univariate analysis found that only the presence of unipolar depression in a spouse of someone with bipolar depression was associated with unipolar depression in offspring, who had a 41.5% risk for developing that disorder. If the spouse was negative for unipolar depression, then the risk in offspring dropped to 24.1% (P <.023). In addition, if the spouse had unipolar depression, then 53.9% of offspring had one or more psychiatric illnesses compared with 31.9% if the spouse did not have unipolar depression.

However, the multiple regression analysis found that when age, country, and gender were considered, unipolar depression in a spouse was no longer independently significantly associated with the risk for illness in offspring while each of these other factors was significantly associated.

More assortative mating also occurred among the parents of the patients (grandparents of the offspring) in the United States (21%) than in Europe (6%), and this also increased the risk for psychiatric illness occurring in the offspring.

The investigators noted that patient-reported diagnoses of spouses, parents, and children is a study limitation, as is the lack of information on disease severity and age of onset of illness in these individuals. However, the researchers suggested that their findings point to the necessity of identifying and treating children at high risk for developing a psychiatric disorder, particularly in the United States.

Reference

Post RM, Altshuler LL, Kupka R, et al. More assortative mating in US compared to European parents and spouses of patients with bipolar disorder: Implications for psychiatric illness in the offspring [published online August 11, 2018]. Eur Arch Psychiatry Clin Neurosci. doi:10.1007/s00406-018-0934-y

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