The recommendations of duration of treatment for alcohol use disorders (AUD) in clinical guidelines are based on consensus decisions. There is a risk that patients will receive too little or too much therapy. We hypothesize that there is an association between duration and effect up until a point where the effects of treatment diminish.

A systematic review and meta-analysis of randomized controlled trials of psychosocial interventions in the alcohol outpatient treatment centers. Population: adults (> 17 years) suffering from AUD treated with at least two sessions of therapy.

Multiple linear regression analysis with outcome measured in percentage of days abstinent (PDA), percentage of heavy days drinking (PHD), drinks per drinking day (DDD) and/or proportion of participants abstinent (ABS) as a function of duration of treatment.

Forty-four studies with 8485 participants were included. Mean duration: 18 (8–82) weeks and 15 (2–36) sessions. Mean follow-up time: 43 (8–104) weeks with a mean of 5 (2–18) research assessments. Only ABS was significantly associated with duration of treatment; ABS increased with 1.6%-point (P < 0.01) with each additional week in treatment. Surprisingly the analysis showed that each research assessment increased PDA with 11%-point (P < 0.001), decreased PHD with 4%-point (P < 0.05) and decreased DDD with 8%-point (P < 0.001).

Duration of treatment was associated positively with proportion of participants abstinent but not percentage of days abstinent drinks per drinking day or percentage of heavy drinking days. The three latter outcomes were affected positively by number of research assessments.

The authors have not supplied their declaration of competing interest.