Tuesday, July 19, 2016

Major depression is more prevalent in urban areas of Canada

Understanding how depression prevalence varies by person, place and time variables can help to plan for services and also generate hypotheses for future research. With respect to planning services an important question is whether there is more depression in urban or rural areas. The evidence so far has been mixed, with a few studies finding an association and others not. A recent analysis of data from a series of Canadian Community Health Surveys was able to incorporate a larger number of observations than any previous study and to settle the issue. The answer is that depression prevalence is about 20% higher in urban areas. This is not a large difference. Some risk factors such as childhood adversities are associated with an approximate doubling (100% increase) in prevalence. Indeed the modest effect of urban living probably explains the previously inconsistent literature. Analyses of individual surveys probably lacked power to detect it. However, from the point of view of planning services, a 18% difference is not trivial. Why would the prevalence be higher in urban areas? There are many possible explanations. One is that the environment there may convey a higher risk of becoming depressed (aka a higher incidence of depression), however, a longer duration of depressive episodes or lower mortality (e.g. due to suicide) in urban areas could also explain it. Finally, migration of depressed people from rural to rural areas is another possible reason for the difference. This work has been published in the Canadian Journal of Psychiatry, a link to the abstract is available here.