Two-year effectiveness of a stepped-care depression prevention intervention and predictors of incident depression in primary care patients with diabetes type 2 and/or coronary heart disease and subthreshold depression; data from the Step-Dep cluster randomized controlled trial

Introduction Major depressive disorders (MDD), diabetes mellitus type 2 (DM2) and coronary heart disease (CHD) are leading contributors to the global burden of disease and often co-occur. Objectives To evaluate the two-year effectiveness of a stepped-care intervention to prevent MDD compared to usual care and to develop a prediction model for incident depression in DM2 and/or CHD patients with subthreshold depression. Methods Data of 236 Dutch primary care DM2/CHD patients with subthreshold depression (Patient Health Questionnaire 9 (PHQ-9) score =6, no current MDD according to the Mini International Neuropsychiatric Interview (DSM-IV criteria)), who participated in the Step-Dep trial were used. A PHQ-9 score of =10 at minimally one measurement during follow-up (at 3, 6, 9, 12 and 24 months) was used to determine the cumulative incidence of MDD. Potential demographic and psychological predictors were measured at baseline via web-based self-reported questionnaires and evaluated using a multivariable logistic regression model. Model performance was assessed with the Hosmer–Lemeshow test, Nagelkerke’s R2 explained variance and Area Under the Receiver Operating Characteristic curve (AUC). Bootstrapping techniques were used to internally validate our model. Results 192 patients (81%) were available at two-year follow-up. The cumulative incidence of MDD was 97/192 (51%). There was no statistically significant overall treatment effect over 24 months of the intervention (OR 1.37; 95% CI 0.52; 3.55). Baseline levels of anxiety, depression, the presence of >3 chronic diseases and stressful life-events predicted the incidence of MDD (AUC 0.80 interquartile range (IQR) 0.79-0.80; Nagelkerke’s R2 0.34 IQR 0.33-0.36). Conclusion A model with four factors predicted depression incidence during two-year follow-up in patients with DM2/CHD accurately, based on the AUC. The Step-Dep intervention did not influence the incidence of MDD. Future depression prevention programs should target patients with these four predictors present, and aim to reduce both anxiety and depressive symptoms.