“Daily supplementation with 248 mg of elemental magnesium as four 500 mg tablets of magnesium chloride per day leads to a significant decrease in depression and anxiety symptoms,” concluded the study team from the Centre for Clinical and Translational Science, Vermont University.
Although observational studies have examined the association between magnesium status and depression, "This is the first randomised clinical trial looking at the effect of magnesium supplementation on symptoms of depression in U.S. adults," explained Emily Tarleton, co-lead author and Bionutrition Research Manager.
The trial was an open-label randomised cross-over trial carried out on adults with mild-to-moderate depression symptoms (scores of 5-19 on the Public Health Questionnaire-9 (PHQ-9)). Enrolment took place over a full year to minimise possible seasonal depression effects.
Six-week supplementation with magnesium chloride reduced PHQ-9 scores by a statistically significant 6.0 points. Generally Anxiety Disorders-7 scores were also reduced by 4.5 points.
The improvements achieved were regardless of age, gender, baseline depression score or use of pharmaceutical antidepressants.
Subjects taking antidepressants concurrently, tended to experience larger decreases in PHQ-9 scores.
A reduction of 5 points in PHQ-9 is recognised as a clinically relevant change in individuals receiving depression treatment, and is used as an efficacy measure of 4-week treatment with pharmaceutical antidepressants.
Most patients who took magnesium experienced improvements within two weeks of starting supplementation. Improvements in depression scores diminished after two weeks of ceasing.
The chloride form of magnesium is readily absorbed and well tolerated by study participants, with the exception of rare cases of diarrhoea. Magnesium is regarded as safe for patients with normal kidney function up to a dose limit of 350 mg elemental magnesium / day (according to US Institute of Medicine guidelines).
Strengths and limitations
Commenting on the strengths and limitations of the trial, the team wrote, “While the cross over design of this trial is robust in controlling for internal biases, it would be reassuring to see the results replicated in larger clinical trials that test long term efficacy and provide additional data on subgroups.”
Such future trials would need to be double-blinded to rule out possible placebo effect in current findings.
Nevertheless, Tarleton enthused"The results are very encouraging, given the great need for additional treatment options for depression, and our finding that magnesium supplementation provides a safe, fast and inexpensive approach to controlling depressive symptoms."
She added that magnesium supplements also have the advantage of lacking the stigma associated with prescription antidepressants, as well as lower risk of side effects.
Widespread adoption of magnesium for depression could also ease the global cost burden on health authorities, given the number of worldwide sufferers exceeds 350 million.