Cytokines, brain-derived neurotrophic factor and C-reactive protein in bipolar I disorder - Results from a prospective study.

•Levels of IL-6 and IL-8 were substantially increased in bipolar disorder as compared with healthy control subjects.•These associations seem to be explained by increased smoking and BMI among patients.•Levels of hsCRP varied according to affective state with higher levels during manic states compared with depressive states.•BDNF, IL-6, IL-8, IL-18 and TNF-α did not vary according to affective states.•This may be due to high doses of atypical antipsychotics and other mood stabilizers that may moderate BDNF and cytokine levels.