OBJECTIVE

To determine whether severity of seasonal depressive symptoms is an independent predictor of depression-specific health service use.

METHODS

Cross-sectional telephone survey evaluating mood-related symptom changes across seasons using a structured interview based on the World Mental Health Composite International Diagnostic Interview, in a community sample representative of the province of Ontario, Canada (N = 1605). This study focuses on the 625 individuals (out of a total of 1605 interviewed) who screened positive for lifetime depressive symptoms. Severity of seasonal symptoms of depression (or "seasonality") was measured using the Seasonal Depression Severity (SDS) score (range 0-36). The primary outcome was lifetime depression-specific use of health services from a physician (family physician or psychiatrist). Lifetime psychotropic medication use, use of health services from a non-physician therapist, and psychiatric hospitalization were secondary outcomes. Other important variables that are known to predict depression-specific health service use were considered in multivariable analysis.

RESULTS

In our sample of individuals with depressive symptoms, those who had used physician health services had higher SDS scores than non-users (11.5 (SD 7.2) vs. 9.7 (SD 6.4), t(616) = 3.182, P = 0.001). In multivariable analysis, SDS score was independently associated with depression-specific health service use by a physician (OR = 1.04, 95% CI 1.01-1.07, p = 0.004). The relationship between seasonality and use of psychotropic medication use was similar (OR = 1.04, 95% CI 1.01-1.07, p = 0.007).

CONCLUSIONS

Seasonality was independently associated with depression-specific health service use for individuals with depressive symptoms. The results imply that greater seasonality may independently reflect increased severity and need for treatment of depression.