Factor Structure of the PHQ-9 Screen for Depression Across Time Since Injury Among Persons With Spinal Cord Injury

Objective: The overlap of somatic-depressive symptoms and physical sequelae of spinal cord injury (SCI) has raised concerns regarding the validity of depression screens used within the SCI population. The Patient Health Questionnaire-9 (PHQ-9) measure parallels Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR ; American Psychiatric Association, 2000 ) criteria of major depression. The authors investigated PHQ-9 factor structure among persons with SCI at various times postinjury. Design: Data from 2,570 participants at 1 year ( N = 682), 5 years ( N = 517), 15 years ( N = 653), and 25 years ( N = 718) postinjury were used. Emergent factors were correlated with satisfaction with life. Results: A 2-factor solution emerged for all groups, with 3 affective referenced items (feeling depressed/hopeless, feeling bad about self/failure, and suicidal ideation) and 3 somatic referenced items (sleep disturbance, low energy/fatigue, and appetite disturbance) loading consistently on Affective and Somatic factors, respectively, at all time points. Factor scores negatively correlated with satisfaction with life. Conclusions: Dual factor structure of the PHQ-9 is present at various times postinjury in the SCI population. It remains unclear whether somatic item endorsement reflects depressive symptomatology per se; however, endorsement is still associated with satisfaction with life.