Long-term effects of melatonin on individuals with depressive, anxiety, or bipolar disorder: a scoping review

Melatonin emerged as a new potential therapeutic agent for the treatment of mood and anxiety disorders. Existing randomized controlled trials (RCTs) have predominantly focused on the immediate effects of melatonin, leaving a knowledge gap concerning its long-term effects.

To conduct a scoping review of the literature in order to collect long-term (≥ 3 months) efficacy and tolerability data of melatonin (agonists) in children, adults, or the elderly with anxiety, depressive, or bipolar disorder.

A systematic literature search of PubMed, Embase, Web of Science, Scopus, and CENTRAL electronic databases was conducted for English or Dutch-language RCTs. Additionally, 3 electronic databases were screened for unpublished clinical trials.

Six hundred sixty-one records were identified as possibly eligible. Of these, six met the inclusion criteria. Although some studies have demonstrated a significant positive long-term effect of melatonin on mood or anxiety symptoms, most have not. In general, the use of melatonin is associated with mild adverse events.

Long-term efficacy data of melatonin (agonists) in patients with mood or anxiety disorders are scarce and inconsistent. There is insufficient long-term data allowing a thorough evaluation of its safety profile.