Twin Study Eyes Inflammation in Those With Bipolar Disorder
Environmental factors may be responsible for proinflammatory monocyte activation
FRIDAY, Sept. 11 (HealthDay News) -- An association between proinflammatory monocytes and bipolar disorder is largely due to a common shared environmental factor, according to research published in the September issue of the Archives of General Psychiatry.
Roos C. Padmos, M.D., of the Erasmus Medical Center in Rotterdam, Netherlands, and colleagues analyzed data from 18 pairs of monozygotic twins and 23 pairs of dizygotic twins (with at least one twin having bipolar disorder), and 18 monozygotic and 16 dizygotic healthy twin pairs. Researchers evaluated a set of 19 genes in their circulating monocytes previously associated with a proinflammatory state.
The authors observed a familial effect on the presence of proinflammatory monocytes, which was likely due mostly to shared environmental factors. Ninety-four percent of the covariance between bipolar disorder and the set of inflammation-related genes was due to shared common environment rather than genetic effects or unique environmental factors, they write.
Several factors might explain a link between bipolar disorder and proinflammatory monocytes, the authors write, including that, "first, bipolar disorder itself induces the proinflammatory state of monocytes (e.g., the stressful state of the illness might induce monocyte activation). Second, the proinflammatory monocytes cause mood disorders in patients (the macrophage theory of depression). Third, there could be a separate underlying factor that influences bipolar disorder as well as monocytes independently from each other (e.g., patients and their family members are present in an infectious/stressful environment that affects both their monocyte systems as well as their brains)."