Favourable short-term outcomes for psychotherapy interventions targeted on depressive patients have been shown, but few studies have examined long-term outcomes in working populations. A group of Finnish investigators used data on recorded sickness absence as an outcome to examine psychotherapy and pharmacotherapy in a large contemporary working population (the 10-Town Study). The eligible population comprised all 67,106 employees of the local government who had been employed for at least 10 months in 1 year between 1994 and 2002.
Three groups were identified: first, those 448 employees who were granted psychotherapy as a treatment for clinically diagnosed depression by the Social Insurance Institution of Finland; second, 3,177 employees treated with antidepressants for at least 12 months during the follow-up, and third, 53,116 healthy controls with no indication of depression. Sickness absence data were obtained from the employers’ registers containing electronic records on the dates of sick leaves for each employee. Only medically certified sick leaves lasting > 21 days were considered, as earlier research suggests a stronger association of long-standing illnesses, such as depression, with sickness absence longer than 21 days than with shorter durations.
For the non-treated employees, the sickness absences were linked to the data in the same manner as for the cases, on the basis of a randomly assigned year. Altogether, 43,966 sick leaves longer than 21 days were recorded for the participants during the 7-year follow-up. A within-group comparison based on Poisson regression analysis with the generalized estimating equations method showed that the rate ratio of sickness absence at the end of the entire follow-up, compared with that during the treatment, was 0.56 for the psychotherapy cases and 0.62 for the antidepressant treatment cases.
For the healthy controls, it was 1.41. For both sexes, absence rates during the treatment were 4.3-6.3 times higher in the psychotherapy and antidepressant groups than among the healthy controls, but 6 years after the end of the treatment they were only 1.9-2.5 times higher. A corresponding pattern was seen for different lengths and combinations of therapies. According to an additional analysis, both the psychotherapy groups and the subgroup treated by antidepressants and additionally confirmed as having clinical depression had a higher rate of sickness absence than the healthy controls. The rate of sickness absence was lower in the psychotherapy group than in the antidepressant subgroup (the overall rate ratio during the 6-year posttreatment period was 0.74).