Description:
<jats:sec id="S0033291717000046_sec_a1"><jats:title>Background</jats:title><jats:p>Substance use may increase the risk of non-adherence to antipsychotics, resulting in negative outcomes in patients with psychosis.</jats:p></jats:sec><jats:sec id="S0033291717000046_sec_a2" sec-type="methods"><jats:title>Method</jats:title><jats:p>We aimed to quantitatively summarize evidence regarding the effect of cannabis use, the most commonly used illicit drug amongst those with psychosis, on adherence to antipsychotic medication. Studies were identified through a systematic database search. Adopting random-effects models, pooled odds ratios (OR) for risk of non-adherence to antipsychotic medications were calculated comparing: cannabis-users at baseline <jats:italic>v.</jats:italic> non-users at baseline; non users <jats:italic>v.</jats:italic> continued cannabis users at follow-up; non-users <jats:italic>v.</jats:italic> former users at follow-up; former users <jats:italic>v.</jats:italic> current users.</jats:p></jats:sec><jats:sec id="S0033291717000046_sec_a3" sec-type="results"><jats:title>Results</jats:title><jats:p>Fifteen observational studies (<jats:italic>n</jats:italic> = 3678) were included. Increased risk of non-adherence was observed for cannabis users compared to non-users (OR 2.46, <jats:italic>n</jats:italic> = 3055). At follow-up, increased risk of non-adherence was observed for current users compared to non-users (OR 5.79, <jats:italic>n</jats:italic> = 175) and former users (OR 5.5, <jats:italic>n</jats:italic> = 192), while there was no difference between former users and non-users (OR 1.12, <jats:italic>n</jats:italic> = 187).</jats:p></jats:sec><jats:sec id="S0033291717000046_sec_a4" sec-type="conclusion"><jats:title>Conclusions</jats:title><jats:p>Cannabis use increases the risk of non-adherence and quitting cannabis use may help adherence to antipsychotics. Thus, cannabis use may represent a potential target for intervention to improve medication adherence in those with psychosis.</jats:p></jats:sec>