The projected effect of risk factor reduction on major depression incidence: A 16-year longitudinal Canadian cohort of the National Population Health Survey

BackgroundFew studies have examined the effect of risk factor modification on depression incidence. This study estimated the effect of risk factor modification on depression incidence.MethodsData analyzed were from the Canadian National Population Health Survey (NPHS) - a longitudinal population-based cohort study. The study followed-up a national cohort sample over a 16-year period from 1994 to 2010. Multivariate modified Poisson regression was used to estimate relative risk.ResultsThe cumulative incidence rate of depression during the 16-year follow-up was 12.07%. Being younger adult, female, Caucasian, poor, occasional/abstainer/former drinker, regular smoker, and having chronic disease were significantly associated with an increased risk of developing depression. About 40% of depression incidence (850,000 cases) was potentially attributable to modifiable risk factors (poor income, smoking, and having a chronic disease). A 10% reduction in the prevalence of these modifiable risk factors could potentially prevent about 165,000 cases of depression.LimitationsThe calculation of PAFs assumes that there is a causal relationship between a risk factor and depression. However, major depression has multiple causes. The potential effect of risk factor modification on depression incidence may vary by the profile of risk factors assessed in a particular study. Several potentially important risk factors were not included in this study.ConclusionPublic health campaigns targeted at significant modifiable risk factors could have a profound effect on future depression incidence. Prevention trials are needed to directly evaluate the effect of single and/or multiple risk factors modification on depression incidence.