People with bipolar disorder (BPD) tend to share similarities in certain characteristics with other members of their families, NIMH-funded researchers have shown. Because the levels of similarity vary from family to family, the findings suggest the existence of different subtypes of BPD and may help determine if the subtypes have different causes.
The researchers reported in the December 2006 issue of the Archives of General Psychiatry that good social functioning "ran in the families" of some people with BPD, and poor social functioning ran in the families of others, with varying levels in between. In either case, the quality of social functioning was among the strongest similarities between members of each family. The researchers also found that about 20 percent of the difference in social functioning had a genetic basis, although influence of shared family environment could not be ruled out as a contributor.
Other characteristics included the levels of substance abuse, alcoholism, psychosis, and suicide attempts within families. As with social functioning, some families tended to share high levels of these characteristics, while other families shared low levels. In either case, the level "ran in the family" of the person with BPD.
Breaking up the broad diagnosis of BPD into subtypes by including these familial characteristics can help researchers untangle the mix of genetic and environmental factors that contribute to this complex disorder. It will, for example, enable researchers to make better decisions about which characteristics to focus on in studies seeking genetic and other biological underpinnings of BPD. Ultimately, this may lead to better diagnosis and treatment.
Francis J. McMahon, MD, and Thomas G. Schulze, MD, of the NIMH Mood and Anxiety Disorders Program, conducted the study with colleagues from the University of Illinois at Chicago, The Johns Hopkins University, and the University of Heidelberg.
Schulze TG, Hedeker D, Zandi P, Rietschel M, McMahon J. What Is Familial About Familial Bipolar Disorder? Archives of General Psychiatry, 63:1368-1376. December 2006.