The present study was undertaken to identify depression subtypes in individuals with or at risk for symptomatic knee osteoarthritis (OA) and to evaluate differences in pain and disability trajectories between groups.
Participants (n = 4,486) were enrolled in the Osteoarthritis Initiative. Latent class analysis was applied to the 20-item Center for Epidemiologic Studies Depression Scale measured at baseline to identify groups with similar patterns of depressive symptoms, and subtypes were assigned using posterior probability estimates. The relationships between depression subtypes and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and disability subscales were modeled over 4 years and stratified by baseline knee OA status (symptomatic [n = 1,626] or at risk [n = 2,860]).
Four subtypes were identified: asymptomatic (80.6%), catatonic (5.3%), anhedonic (10.6%), and melancholic (3.5%). Catatonic and anhedonic subtypes were differentiated by symptoms corresponding to psychomotor agitation and the inability to experience pleasure, respectively. The melancholic subtype expressed symptoms related to reduced energy and movement, anhedonia, and other somatic symptoms. Detectable mean differences in pain and disability compared to the asymptomatic group were observed for the anhedonic (1.5-2.3 WOMAC units) and melancholic (4.8-6.6 WOMAC units) subtypes, and associations were generally larger in individuals with symptomatic knee OA relative to those at risk.
Among individuals with or at risk for symptomatic knee OA, there is evidence of depression subtypes characterized by distinct clusters of depressive symptoms that have differential effects on reports of pain and disability over time. Our findings thus imply that depression interventions could be optimized by targeting the specific symptomology that these subtypes exhibit.