Factor structure of a combined measure of major depressive disorder and male depression in prostate cancer patients

Abstract

Significant numbers of prostate cancer (PCa) patients become depressed [1], but treatment of this depression is inconsistently effective [2]. One possible reason for that inconsistency could be inadequate assessment of depression in PCa patients because most scales do not recognise the specific extra symptoms that comprise 'male' depression [3]. The authors of the Gotland Scale of Male Depression (GSMD) [4] identified those extra symptoms of male depression as aggression, irritability and alcohol use, not included in major depressive disorder (MDD) [5]. Therefore, a previous study [6] suggested that male depression might be measured by combination of the first nine items of the Patient Health Questionnaire-9 (PHQ-9) [7] (which diagnoses MDD) plus those items from the GSMD that are not included in the PHQ-9. This combined scale was called the PHQ9-GSMD but, although either a one-factor solution or a two-factor solution has been reported for the PHQ-9 [8] (but not on PCa patients) and a single-factor structure for the GSMD [9] (also not on PCa patients), the factor structure of the combined PHQ9-GSMD has not been reported. Description of this factor structure may contribute to more targeted interventions that may increase the efficacy of treatment for PCa depression, and this was the aim of the present study.