Impact of clinical pharmacist interventions in psychiatric hospitals on clinical and medication-related outcomes: a systematic review and meta-analysis

Introduction Clinical pharmacist interventions have been shown to improve outcomes and reduce drug-related problems (DRPs) in patients with mental disorders. However, no previous meta-analysis has comprehensively evaluated their effectiveness in reducing DRPs and optimizing pharmacotherapy in psychiatric inpatient settings. Aim To evaluate the effectiveness of clinical pharmacist interventions in psychiatric inpatient settings on DRPs and clinical outcomes among patients with mental disorders. Methods This systematic review and meta-analysis was conducted according to the PRISMA 2020 statement and prospectively registered in PROSPERO (CRD420261309290). PubMed, Scopus, CENTRAL, and CINAHL were searched from inception to March 2026. Eligible studies included adult psychiatric inpatients receiving clinical pharmacist interventions, including different pharmaceutical services, such as medication review, medication reconciliation, and ward round participation. A meta-analysis was performed in R using a random-effects model. Heterogeneity was calculated using I 2 . Random-effects meta-analyses were performed for DRPs, potentially inappropriate medications (PIMs), and the number of prescribed medications. Risk of bias was assessed using RoB two and ROBINS-I. Results Eighteen studies met the inclusion criteria, including one randomized controlled trial and 17 non-randomized interventional studies. Clinical pharmacist interventions significantly reduced the number of prescribed medications (mean difference −1.0 medications per patient, (95% CI −1.5 to −0.5) and were associated with a pooled reduction in DRPs of 70.7% (95% CI 46.5–87.0), as well as reductions in PIMs. Evidence for patient-centred clinical outcomes, including symptom improvement, quality of life, and healthcare utilization, remained limited. Substantial heterogeneity was observed across studies, reflecting differences in intervention types, patient populations, and outcome measures. Most non-randomized studies were judged to have a serious risk of bias because of confounding and uncontrolled study designs. Conclusion Clinical pharmacist interventions in psychiatric inpatient settings improve medication-related outcomes by reducing DRPs, PIMs, and the number of prescribed medications. These findings support the integration of clinical pharmacists into multidisciplinary psychiatric teams. Further adequately powered multicentre randomized controlled trials are needed to determine whether these improvements translate into better long-term patient-centred clinical outcomes.