Updated adjunctive minocycline for schizophrenia: A systematic review and meta-analysis of clinical and cognitive...

Minocycline has been proposed as an adjunctive treatment for schizophrenia due to its anti-inflammatory and neuroprotective properties. However, evidence regarding its efficacy across clinical and cognitive outcomes remains inconsistent.

A systematic review and meta-analysis of double-blind RCTs was conducted following PRISMA guidelines. PubMed, Web of Science, Embase, Ovid MEDLINE, and the Cochrane Library were searched from January 2000 to August 2025. Eligible studies included patients with schizophrenia receiving adjunctive minocycline plus stable antipsychotics. Primary outcomes were PANSS total and subscale scores and overall cognitive performance. Secondary outcomes included SANS, CDS, CGI, GAF, and seven cognitive domains. Standardized mean differences (SMDs) with 95% CIs were calculated.

Ten RCTs involving 895 participants were included. Adjunctive minocycline was associated with improvements in negative symptoms (PANSS negative: SMD = -0.55, 95% CI: -0.96 to -0.13; SANS: SMD = -0.75, 95% CI: -1.00 to -0.49) and overall psychopathology (PANSS total: SMD = -0.49, 95% CI: -0.80 to -0.18). Cognitive benefits were limited to a modest improvement in working memory (SMD = 0.24, 95% CI: 0.08 to 0.39), with no significant effects in other cognitive domains. Subgroup analyses suggested that illness stage, antipsychotic regimen, treatment duration, sample size, and geographic region may contribute to variability in treatment effects. Adverse event rates were comparable between groups.

Adjunctive minocycline may improve negative symptoms and provide modest working memory benefits in schizophrenia. However, the evidence is limited by substantial heterogeneity, potential small-study effects, and inconsistent findings. Although short- to medium-term tolerability appeared comparable to placebo, larger, longer-term RCTs are needed to confirm its efficacy and safety.