The siblings of patients with bipolar disorder not only face a significantly increased lifetime risk of that affective disorder, but a whole panoply of other psychiatric disorders, according to a new Danish longitudinal national registry study.
“Our data show the healthy siblings of patients with bipolar disorder are themselves at increased risk of developing any kind of psychiatric disorder. Mainly bipolar disorder, but all other kinds as well,” Lars Vedel Kessing, MD, DMSc, said in presenting the results of the soon-to-be-published Danish study at the virtual congress of the European College of Neuropsychopharmacology.
Moreover, the long-term Danish study also demonstrated that several major psychiatric disorders follow a previously unappreciated bimodal distribution of age of onset in the siblings of patients with bipolar disorder. For example, the incidence of new-onset bipolar disorder and unipolar depression in the siblings was markedly increased during youth and early adulthood, compared with controls drawn from the general Danish population. Then, incidence rates dropped off and plateaued at a lower level in midlife before surging after age 60 years. The same was true for somatoform disorders as well as alcohol and substance use disorders.
“Strategies to prevent onset of psychiatric illness in individuals with a first-generation family history of bipolar disorder should not be limited to adolescence and early adulthood but should be lifelong, likely with differentiated age-specific approaches. And this is not now the case.
“Generally, most researchers and clinicians are focusing more on the early part of life and not the later part of life from age 60 and up, even though this is indeed also a risk period for any kind of psychiatric illness as well as bipolar disorder,” according to Dr. Kessing, professor of psychiatry at the University of Copenhagen.
Dr. Kessing, a past recipient of the Brain and Behavior Research Foundation’s Outstanding Achievement in Mood Disorders Research Award, also described his research group’s successful innovative efforts to prevent first recurrences after a single manic episode or bipolar disorder.
Danish national sibling study
The longitudinal registry study included all 19,995 Danish patients with a primary diagnosis of bipolar disorder during 1995-2017, along with 13,923 of their siblings and 278,460 age- and gender-matched controls drawn from the general population.
The cumulative incidence of any psychiatric disorder was 66% greater in siblings than controls. Leading the way was a 374% increased risk of bipolar disorder.
Strategies to prevent a first relapse of bipolar disorder
Dr. Kessing and coinvestigators demonstrated in a meta-analysis that, with current standard therapies, the risk of recurrence among patients after a single manic or mixed episode is high in both adult and pediatric patients. In three studies of adults, the risk of recurrence was 35% during the first year after recovery from the index episode and 59% at 2 years. In three studies of children and adolescents, the risk of recurrence within 1 year after recovery was 40% in children and 52% in adolescents. This makes a compelling case for starting maintenance therapy following onset of a single manic or mixed episode, according to the investigators.