High Dose Vitamin B6 Reduces Depression Symptoms

Several lines of evidence suggest that vitamin B6 has potential as an antidepressant. It plays a crucial coenzyme role in the synthesis of the neurotransmitters serotonin, gamma-aminobutyric acid (GABA) and dopamine, which are central to mood regulation, and it has been shown that increasing availably of vitamin B6 above normal levels increases concentrations of serotonin and GABA. Furthermore, epidemiological evidence points to vitamin B6 deficiency as a risk factor for depression, and to high vitamin B6 levels as protective. Therefore, we asked whether taking 100 mg vitamin B6 as pyridoxine daily for 1 month would reduce depression symptoms, measured with the Depression, Anxiety and Stress Scales (DASS) questionnaire, which also assesses anxiety and stress.

We recruited 267 participants from the general population (215 female) and double blind randomised them to receive either placebo, vitamin B6 or vitamin B12 (1000 µg). Using baseline DASS scores, we divided participants into a group classified as having mild or more severe depression symptoms at baseline (N = 58) and a larger group classified as non-depressed.

Only within the former group, vitamin B6 produced a selective reduction in depression symptoms compared to placebo or vitamin B12 with a very large effect size (partial η ² = 0.20). We also found evidence that participants whose DASS depression scores narrowly failed to meet criterion for moderate depression (N = 52) experienced a slightly smaller but still statistically substantial reduction in symptoms (partial η ² = 0.17). We repeated the analysis procedure for anxiety and stress scores but found no significant effects.

We have shown that high-dose vitamin B6 has therapeutic potential for depression, and large-scale clinical trials with patients should now be conducted to determine whether these findings from our mostly female sample generalise to males, to quantify the dose-response relationship, and to evaluate its potential as an adjunct to existing treatments versus monotherapy, and to elucidate which factors, for example, presence of inflammation, predict responsiveness to the intervention.