Psychotherapy duration and work disability: A prospective Finnish register study

The influence of psychotherapy duration on common mental disorder (CMD) outcomes remains a topic of ongoing debate. Whereas most research has focused on CMD symptom change, the evidence on the psychotherapy duration of subsequent CMD-related work disability and the change in psychotropic drug purchases is scarce.

We used a register-based cohort representing 33% of the Finnish population. The participants included working-age individuals (N = 12,047, 76% women, mean age = 36) who initiated long-term psychotherapy, between 2014 and 2017. They were followed from 2011 to 2021 and psychotherapy duration ranged from less than a year to over 3 years. We used an interrupted time series design to analyze the psychotherapy duration-dependent changes in CMD-related work disability (primary outcome, operationalized as depression or anxiety-related sickness absence, SA, days) and the annual number of psychotropic drug purchases or distinct drugs purchased (secondary outcomes).

There were no differences in the levels of work disability or drug purchases before the psychotherapy. We observed a decreasing level and trend in all outcomes across all psychotherapy duration groups. The largest decline in level was observed in the <1-year duration group (88% decline for SA and 43%-44% for drug purchases) while the smallest decline was in the 3+ years duration group (73% for SA and 27% for drug purchases).

Work disability outcomes and duration varied among individuals, even with similar initial mental health-related work disability or use of auxiliary psychotropic treatments. Compared to longer psychotherapy, shorter psychotherapy was associated with sharper improvements.