Wednesday, October 12, 2016

Major Depression is More Common in More Northerly Latitudes in Canada

Major depression is thought to be more common in the winter than the summer months in Canada (e.g. follow this link), and changing circadian patterns are believed to have a role in this. It has sometimes been suspected that there would be a north-south latitude gradient as well. However, the small number of studies that have looked at this have failed to find an association, see Partonen et al. and Grimaldi et al.  Using data from many large scale Canadian surveys, were able to examine this association with a much larger sample size than was previously possible. These surveys included a measure of past year major depressive episodes called the Composite International Diagnostic Interview, Short Form and by linking to postal code files we were able to determine the approximate latitude of each respondent. A small gradient was found, with more northerly latitudes having a higher prevalence. A link to be the abstract is available here. It is possible that the etiology of such depression is related to factors such as sunlight exposure or shifting circadian patterns with more northerly latitudes. Of course, the difference could also be due to social determinants. Additional studies will be needed to determine this, but with adjustment for many potential determinants (age, sex, marital status, income, education) the association persisted. These results may contain clues to understanding the causes of depression more clearly, but they certainly also have implications for planning health services in more northerly places.

1 comment:

Linda said...

You have a great blog. Warm greetings from Montreal, Canada. I have struggled with depression for decades now (I just turned 60 on October 27th). I find that I can struggle with depression even in the summer, as the summers here in Montreal can get very hot and humid, and since I don't take this kind of heat very well, I don't take my nature walks as much as I would in these conditions and, when I do, I take walks in a mall, where it is safer and cooler. I find that my long walks in nature help me quite a big...that, plus doing my blog, which I find both to be very therapeutic. If you take a look at my blog you will see why I find blogging to be good therapy. I do my best to focus on the positive, laughter and good music.