Bright light for nonseasonal depression?

Seasonal variation in major depressive episode prevalence in Canada

BACKGROUND

The purpose of this paper is to describe variation, over the months of the year, in major depressive episode (MDE) prevalence. This is an important aspect of the epidemiological description of MDE, and one that has received surprisingly little attention in the literature. Evidence of seasonal variation in MDE prevalence has been weak and contradictory. Most studies have sought to estimate the prevalence of seasonal affective disorder using cut-points applied to scales assessing mood seasonality rather than MDE. This approach does not align with modern classification in which seasonal depression is a diagnostic subtype of major depression rather than a distinct category. Also, some studies may have lacked power to detect seasonal differences. We addressed these limitations by examining the month-specific occurrence of conventionally defined MDE and by pooling data from large epidemiological surveys to enhance precision in the analysis.

METHOD

Data from two national survey programmes (the National Population Health Survey and the Canadian Community Health Survey) were used, providing ten datasets collected between 1996 and 2013, together including over 500,000. These studies assessed MDE using a short form version of the Composite International Diagnostic Interview (CIDI) for major depression, with one exception being a 2012 survey that used a non-abbreviated version of the CIDI. The proportion of episodes occurring in each month was evaluated using items from the diagnostic modules and statistical methods addressing complex design features of these trials. Overall month-specific pooled estimates and associated confidence intervals were estimated using random effects meta-analysis and a gradient was assessed using a meta-regression model that included a quadratic term.

RESULTS

There was considerable sampling variability when the month-specific proportions were estimated from individual survey datasets. However, across the various datasets, there was sufficient homogeneity to justify the pooling of these estimated proportions, producing large gains in precision. Seasonal variation was clearly evident in the pooled data. The highest proportion of episodes occurred in December, January and February and the lowest proportions occurred in June, July and August. The proportion of respondents reporting MDE in January was 70% higher than August, suggesting an association with implications for health policy. The pattern persisted with stratification for age group, sex and latitude.

CONCLUSIONS

Seasonal effects in MDE may have been obscured by small sample sizes in prior studies. In Canada, MDE has clear seasonal variation, yet this is not addressed in the planning of services. These results suggest that availability of depression treatment should be higher in the winter than the summer months.

Bright light therapy in the treatment of childhood and adolescence depression, antepartum depression, and eating disorders

Circadian rhythm disorders represent an important component underlying the pathology of depression. One of the subtypes of depression, in which these disorders may play a crucial role, is the seasonal affective disorder (SAD). The bright light therapy (BLT) has been reported as a novel, promising treatment method for SAD since 1984, and most of the data revealing its efficacy has been referred to adult patients, without comorbid disorders. However, in the recent years, more and more reports have been presented, which confirm the usefulness of BLT in some specific subpopulations of patients, including children, adolescents and pregnant women. The present review summarizes the applications of BLT in antepartum depression, childhood and adolescence depression as well as in patients suffering from eating disorders. Although the body of evidence is still too small to recommend the use of BLT as the first line of treatment for the depression or eating disorders in these patient subpopulations; it appears that BLT may be a useful alternative or adjunctive therapy for these diseases. However, the specific clinical applications of BLT in these areas need further investigation.