Improvement in depressive symptoms in people undergoing cognitive behavioral therapy who supplemented with...

Major Depressive Disorder (MDD) is a prevalent condition affecting 4% of the population, resulting in significant functional impairment from biopsychosocial factors. Cognitive Behavioral Therapy (CBT) is considered the first choice followed by pharmacotherapy. Probiotics have been investigated to treat symptoms of MDD. This quasi-experimental, open-label study aims to evaluate the effect of probiotic blend supplementation on depressive and anxiety symptoms and biomarkers in depressive patients undergoing pharmacotherapy and CBT.

Adult individuals diagnosed with MDD attending a primary healthcare unit received pharmacotherapy, CBT and probiotics supplementation. Patients who agreed were allocated to interventions and followed up for six months, with three assessments of clinical scales and biomarkers. Probiotics supplementation was introduced at time 1 (4.7 ± 0.3 months after CBT initiation) and maintained for 1.95 ± 0.2 months.

Probiotics with CBT decreased anxiety and depressive symptoms, followed by an increase at the end of the study (P < 0.001). Serum BDNF levels increased across time (P < 0.001). This effect was not observed for lactate, hs-CRP, IL-6, IL-10, TNF-α, NO or NGF-β levels. Following the probiotic period (time 2), Spearman's correlation demonstrated a significant negative correlation between both anxiety and depression symptoms and IL-6 levels (P < 0.05). A negative association was observed between depression scores and BDNF (P < 0.01).

Anxiety and depression symptoms were significantly reduced through continuous CBT combined with probiotic blend supplementation. However, this beneficial effect on symptoms did not persist in all patients after probiotic discontinuation. In contrast, the accompanied increase in serum BDNF levels remained elevated for all patients, even after cessation. The significance of this combined effect remains evident despite limitations such as the small sample size and the sequential design, supporting the microbiota-homeostasis hypothesis in MDD.