Brain-derived neurotrophic factor (BDNF), which facilitates neuroplasticity and synaptogenesis, may be decreased in bipolar disorder, but has not been systematically investigated in people with newly diagnosed bipolar disorder and unaffected first-degree relatives.

To compare BDNF levels in patients with newly diagnosed bipolar disorder, their unaffected first-degree relatives and healthy controls.

The study investigated plasma BDNF levels in patients (n = 371) with newly diagnosed bipolar disorder, their unaffected first-degree relatives (n = 98) and healthy controls (n = 200) using enzyme-linked immunosorbent assay. We further investigated associations between BDNF levels and illness-related variables and medication status.

BDNF levels were found to be 22.0% (95% CI 1.107–1.343) higher in patients with bipolar disorder compared with healthy controls (P < 0.001) and 15.6% higher in unaffected first-degree relatives compared with healthy controls (95% CI 1.007–1.327, P = 0.04), when adjusting for age and gender. Further, BDNF levels were positively associated with duration of illness at a trend level (P = 0.05), age (P = 0.001) and use of anti-epileptic medication (P = 0.05).

These findings suggest that BDNF levels are not decreased in the early stages of bipolar disorder and in unaffected first-degree relatives contrasting with prior findings during later stages of the illness.

Changes in inflammatory and metabolic markers are implicated in the pathogenesis in both the development and progression of bipolar disorder (BD). Notwithstanding, these markers have not been investigated in newly diagnosed BD.

We compared high-sensitive C-reactive protein (hs-CRP) and homocysteine (Hcy) levels in 372 patients with newly diagnosed BD, 106 unaffected first-degree relatives (URs), and 201 healthy control persons (HCs). Within the patient group, we also investigated possible associations between hs-CRP and Hcy, respectively, with illness-related characteristics and psychotropic medication.

No statistically significant differences in Hcy and hs-CRP levels were found when comparing BD and URs with HCs. Similarly, there were no differences when comparing only patients in remission or patients with affective symptoms, respectively, with HCs. Hcy levels were found to be 11.9% (95% CI: 1.030–1.219) higher in patients with BD when compared with their URs (p = 0.008), when adjusting for folate and cobalamin status, age, sex, and self-reported activity levels. Hcy levels were significantly associated with folate, cobalamin, gender, and age in all models (p < 0.05).

Our results do not support hs-CRP or Hcy as markers in newly diagnosed BD.