Understanding the Relationship Between Depression Symptom Severity and Health Care Costs for Patients With...

To examine whether measures of depression symptom severity could improve understanding of health care costs for patients with major depressive disorder (MDD) or treatment-resistant depression (TRD) from the health plan perspective.

In this retrospective cohort study within an integrated health system, cohorts consisted of 2 mutually exclusive groups: (1) adults with TRD based on a standard treatment algorithm and (2) adults with MDD, but no TRD, identified through ICD-9/10-CM codes. Depression severity was measured using the Patient Health Questionnaire-9 (PHQ-9). Patterns of health care resource utilization (HRU) and costs were compared between the TRD and MDD groups overall and within the groups at different symptom levels. A general linear model with a γ distribution and log link for cost outcomes, logistic regression for binary outcomes, and negative binomial regression for count outcomes were used.

Patients with TRD (n = 24,534) had greater comorbidity than those in the MDD group (n = 17,628). Mean age in the TRD group was 52.8 years versus 48.2 for MDD (P < .001). Both groups were predominantly female (TRD: 72.8% vs MDD: 66.9%; P < .001). Overall, the TRD group had greater costs than the MDD group, with 1.23 times (95% CI, 1.21-1.26; P < .001) greater total cost on average over 1 year following index date. Within both groups, those with severe symptoms had greater total mean (SD) costs (TRD: moderate: $12,429 [$23,900] vs severe: $13,344 [$22,895], P < .001; low: $12,220 [$31,864] vs severe: $13,344 [$22,895], P < .001; MDD: moderate: $8,899 [$20,755] vs severe: $10,098 [$22,853]; P < .001; low: $8,752 [$25,800] vs severe: $10,098 [$22,853], P < .001).

MDD and TRD impose high costs for health systems, with increasing costs as PHQ-9 symptom severity rises. Better understanding of subgroups with different symptom levels could improve clinical care by helping target interventions.