Twenty-nine studies (2,467 participants) were included in the review. None of the studies were considered to be low risk of bias for the outcome of psychostimulant abstinence. Three studies had a low risk of bias for treatment retention. Most studies did not report methods of sequence generation or allocation concealment and had high attrition (psychostimulant outcome). Blinding was fulfilled for both outcomes.
IDAs were associated with a statistically significant reduction in psychostimulant use compared to placebo (SMD 0.20, 95% CI 0.06 to 0.35; 22 studies, moderate heterogeneity, I2=25%). There was no evidence of publication bias. There was no statistically significant difference between IDA and placebo for treatment retention (28 studies, no heterogeneity), although retention was higher in dual heroin-cocaine dependent patients who received opioid maintenance treatment.
Sensitivity analyses did not materially alter the main findings. Subgroup analyses for psychostimulant dependence indicated that dexamphetamine and bupropion were individually superior to placebo. Similar effect sizes were noted for IDAs with and without a psychostimulant effect. IDAs were statistically efficacious for patients with cocaine dependence and the effect was moderate for those with dual opioid-psychostimulant dependence. There was a positive correlation between treatment length and IDA efficacy. There were no statistically significant findings in subgroup analyses for treatment retention and there was no correlation here between treatment length and IDA efficacy. No analysis in relation to risk of bias was conducted.