New research into bipolar I disorder (BPI) suggests the existence of an externalizing disorder subphenotype within BPI with greater severity of mood disorder and possible specific genetic features that differ from standard bipolar, according to a study published in the Journal of Affective Disorders.
Shanker Swaminathan, Ph.D., of Indiana University, Indianapolis, and his associates analyzed a cohort of 2,505 patients with bipolar I, taken from the National Institute of Mental Health (NIMH) Bipolar Disorder Genetics Initiative over 18 years and split into nonexternalizing and externalizing groups.
They noticed increased severity and frequency of mood disorder symptoms and episodes in the externalizing group, particularly in the early-onset externalizing subgroup. For example, nonsuicidal self-harm was seen in 30.2% of early-onset subjects, compared to 10% of nonexternalizing subjects (and 26% of externalizing subjects as a whole). Rapid switching was seen in 70.6% of early-onset subjects, compared to 48.6% of nonexternalizing subjects (and 62.8% of externalizing subjects as a whole), reported Dr. Swaminathan.
“In every parameter tested, subjects with externalizing disorders show evidence of greater symptomatology, earlier onset, and more impairment. This is true even when care is taken to exclude the direct effects of substances,” the authors wrote.
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