What do systematic reviews say?

Metformin vs placebo

Metformin showed no clear difference in drop‐outs (12 to 14 weeks) compared with placebo (moderate certainty).

• Interventions for preventing type 2 diabetes in adults with mental disorders in low‐ and middle‐income countries 2021 · Cochrane Headline outcomes only
  RR 1.22 [0.09, 16.35]
  3 studies · 158 participants
  Moderate