What do systematic reviews say?

Melatonin vs placebo

Melatonin showed no clear difference in drop‐outs (8 weeks) compared with placebo (low certainty).

• Interventions for preventing type 2 diabetes in adults with mental disorders in low‐ and middle‐income countries 2021 · Cochrane Headline outcomes only
  RR 1 [0.38, 2.66]
  1 study · 48 participants
  Low