Abstract: We included 17 studies involving 8787 participants: nine in multidisciplinary mental health care, six in psychological therapy settings, and two in primary care. Pooling of outcome data to provide a summary estimate of effect across studies was possible only for those studies using the compound Outcome Questionnaire (OQ-45) or Outcome Rating System (ORS) PROMs, which were all conducted in multidisciplinary mental health care or psychological therapy settings, because both primary care studies identified used single symptom outcome measures, which were not directly comparable to the OQ-45 or ORS. Meta-analysis of 12 studies including 3696 participants using these PROMs found no evidence of a difference in outcome in terms of symptoms, between feedback and no-feedback groups (standardised mean difference (SMD) -0.07, 95% confidence interval (CI) -0.16 to 0.01; P value = 0.10). The evidence for this comparison was graded as low quality however, as all included studies were considered at high risk of bias, in most cases due to inadequate blinding of assessors and significant attrition at follow-up. Quality of life was reported in only two studies, social functioning in one, and costs in none. Information on adverse events (thoughts of self-harm or suicide) was collected in one study, but differences between arms were not reported. It was not possible to pool data on changes in drug treatment or referrals as only two studies reported these. Meta-analysis of seven studies including 2608 participants found no evidence of a difference in management of CMHDs between feedback and no-feedback groups, in terms of the number of treatment sessions received (mean difference (MD) -0.02 sessions, 95% CI -0.42 to 0.39; P value = 0.93). However, the evidence for this comparison was also graded as low quality. We found insufficient evidence to support the use of routine outcome monitoring using PROMs in the treatment of CMHDs, in terms of improving patient outcomes or in improving management. The findings are subject to considerable uncertainty however, due to the high risk of bias in the large majority of trials meeting the inclusion criteria, which means further research is very likely to have an important impact on the estimate of effect and is likely to change the estimate. More research of better quality is therefore required, particularly in primary care where most CMHDs are treated. Future research should address issues of blinding of assessors and attrition, and measure a range of relevant symptom outcomes, as well as possible harmful effects of monitoring, health-related quality of life, social functioning, and costs. Studies should include people treated with drugs as well as psychological therapies, and should follow them up for longer than six months.

Plain-language summary: Routine outcome monitoring of CMHDs using PROMs was not shown conclusively to be helpful in analyses combining study results, either in terms of improving patient symptom outcomes (across 12 studies), or in changing the duration of treatment for their conditions (across seven studies). It was not possible to analyse changes in drug treatment or referrals for further treatment as only two studies reported these. Similarly, health-related quality of life, social functioning, adverse events, and costs were reported in very few studies. More research of better quality is required, especially in primary care where most CMHDs are treated. Studies should include people treated with drugs as well as psychological therapies, and should follow them for longer than six months. As well as symptoms and length of treatment, studies should measure possible harms, quality of life, social functioning, and the costs of monitoring.