Psychotherapy duration and work disability: A prospective Finnish register study.

INTRODUCTION: 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.

METHODS: 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).

RESULTS: 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).

CONCLUSION: 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.