Attrition rates in trials for adolescents and young adults at clinical high-risk for psychosis: A systematic review and meta-analysis

Background: Treatment of those at clinical high-risk (CHR) for developing psychosis may lead to preventive strategies. However, attrition in trials may hamper efforts to detect effective changes and lead to bias. Our objective was to synthesize the relative attrition rates in clinical trials conducted in CHR for psychosis samples.

Method: We searched the following electronic databases: MEDLINE, Embase, PsycINFO, CINAHL and EBM with no restrictions. Inclusion criteria was any treatment-based randomized controlled trial (RCT) conducted in CHR samples that reported attrition. Relative attrition rates were calculated using random-effects meta-analysis, stratified by time, and reported as odds ratios (ORs), proportions, and 95% confidence intervals (CIs).

Results: Twenty-one RCTs met our inclusion criteria, including a total of 2260 CHR participants. Attrition rates between all treatment types identified were not statistically different from control treatments at any time-point. When accessing overall trial attrition, the pooled attrition rate was 29.57% (95% CI = 23.84-35.63%) with statistically significant heterogeneity (I² = 88.70%; P < .001). Furthermore, 11 trials had a subsequent follow-up after the intervention was conducted and the pooled attrition was 33.96% (95% CI = 24.94-43.59%). When examining predictors of attrition, no statistically significant subgroup differences were observed in attrition rates.

Conclusions: Almost one third of CHR participants will not complete participation in an RCT, however no predictors were found to be statistically significantly related to attrition. Methods to account for missing data and attrition are warranted in CHR trials to account for potential biases associated with high attrition rates.