Background: Studies of psychological interventions for the prevention of depression have found significant effects in the short-term, but the long-term efficacy has yet to be determined. This study evaluated the 8-year effect of a randomized controlled trial for indicated prevention of depression in female caregivers.
Methods: A total of 173 non-professional female caregivers with subclinical depressive symptoms not meeting criteria for a major depressive episode (MDE) were randomized to either a brief problem-solving intervention (n = 89) or usual-care control group (n = 84). Blinded evaluators conducted an assessment at the 8-year follow-up. The primary outcome was Depression Status, defined by diagnoses of MDE since the 1-year follow-up using the Structured Clinical Interview for the Disorders of the DSM-5. The secondary outcome was current Depressive Symptom Severity. Regression analyses were conducted to evaluate the effect of the intervention on the outcomes.
Results: There were no significant differences in the Depression Status between the problem-solving (30.3%) and control groups (26.2%) (adjusted OR 1.25, 95% CI -0.58 to 2.69). Depressive Symptom Severity, however, was significantly lower in the problem-solving group compared to the control group at this follow-up, amounting to a small effect size of Cohen's d = 0.39 (adjusted B = -3.32, p = 0.018).
Conclusions: This is the first study to assess such a long-term follow-up of intervention of indicated prevention of depression. Results seem to indicate that the protective effect of the intervention became smaller over time during follow-up. Future research should replicate these results.
Keywords: Caregiver; cognitive-behavioural therapy; depression; prevention; problem-solving; randomized controlled trial.