Vitamin B12 may play a role in how well people with depression respond to antidepressant drugs, new research from Finland suggests.
In a study of people being treated for depression, participants with higher levels of vitamin B12 tended to get a greater benefit from antidepressants, researchers report.
The researchers note that it is still too early to suggest that people with depression take vitamin B12 or other vitamin supplements to treat depression. But the results of the study do justify future trials to test the effect of vitamins in combination with antidepressants, particularly since many patients with depression do not respond to current treatments.
Several studies have found low levels of vitamin B12 and the B vitamin folate in people with depression. Some research has suggested that levels of vitamin B12 and folate influence the effectiveness of antidepressants, but the evidence is not conclusive.
In this study, researchers measured levels of vitamin B12 in the blood of 115 people who had major depressive disorder. All of them were being treated for depression during the 6-month study.
Levels of vitamin B12 were directly related to the odds of treatment success, with those who responded fully to antidepressant treatment having the highest levels of B12 at both the beginning and end of the study. Levels of the vitamin were next highest in people who had a partial response to antidepressant medication and were lowest in those who did not respond at all.
The relationship between vitamin B12 levels and treatment success persisted even after the researchers took into account other factors that could have influenced the results, including age, sex, duration of depression, smoking habits and severity of depression.
Folate levels were not significantly associated with treatment outcome once these factors were considered.
Exactly how vitamin B12 may affect treatment outcome is uncertain. One possibility, according to researchers, is that vitamin B12 is needed to form substances called monoamines that are found in the central nervous system. Antidepressants increase the activity of monoamines, so higher levels of vitamin B12 may boost the drugs' efficiency by promoting the synthesis of monoamines.
Another theory is that a deficiency in vitamin B12 may promote the accumulation of a protein called homocysteine, which may enhance depression.
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