Tuesday, February 24, 2015

Epidemiology for Canadian Students

I have been teaching the Fundamentals of Epidemiology more or less continuously at the University of Calgary since the early 1990s. I have always been frustrated by the lack of a text book that emphasizes (or even mentions) the main sources of data that students of epidemiology in Canada will use during their careers. For this reason, I have written an introductory textbook that I hope Canadian students will find useful. For more information, click here. In addition to emphasizing (not exclusively) the Canadian context, there are a couple of features that have been emphasized. One is that each chapter is divided into two parts. The first part provides basic content and the second, called "thinking deeper" delves a little deeper into a more advanced topic related to that chapter. In this way, I have attempted to make the book appealing both for undergraduate students and graduate students. Second, rather than reserving the topic of bias, which is a difficult topic for complex parameters such as odds ratios or risk ratios, this topic is addressed in chapters focusing on simpler parameters, such as prevalence. I hope that this will make some of the most difficult topics for introductory students (selection bias in analytical studies, differential versus non-differential misclassification bias) more accessible since they can first master the concepts in a simpler form.

Saturday, February 7, 2015

Updated epidemiological information on depression in Canada - good news or bad?

In the January 2015 issue of the Canadian Journal of Psychiatry we published some updated information on major depression epidemiology in Canada. These new estimates come from a survey called the CCHS-MH, which employed an adaptation of the World Health Organization World Mental Health Composite International Diagnostic Interview and had a sample of n = 25 113. Previously, national estimates were only available from a 2002 survey (the CCHS 1.2) or from studies using a short-form version of the diagnostic interview. Among survey respondents with past-year MDD, 63.1% had sought treatment and 33.1% were taking an antidepressant (AD). This report confirms prior results indicating that antidepressant use has stopped increasing in Canada, however, an encouraging sign is that treatment-seeking appears to have increased. There are frequent assertions that only a minority of people with major depression seek treatment, but this is no longer the case in Canada. It is likely that there have been increases in treatments other than antidepressant medication, such as psychotherapy or second-generation antipsychotic medications, however, additional studies are needed to confirm these hypotheses. The 2012 survey also provided an initial opportunity to examine comorbidity between major depression and alcohol abuse and dependence. The earlier national mental health survey (conducted by Statistics Canada in 2002) was unable to assess abuse and dependence due to the measurements instrument selected for that survey. In the 2012 survey 4.8% had past-year alcohol abuse and 4.5% had alcohol dependence. In the same issue, we apply some quantitative data synthesis techniques to pool estimates of major depression prevalence across many surveys that have looked at this in Canada's national population. We used a meta-regression technique to determine whether there was an increase in major depression prevalence, finding the slope not to significantly differ from zero, indicating no-change in prevalence. The abstract for the paper is available here. Is this good news or bad news? It does combat the notion that there is an epidemic of depression in Canada, e.g. see here, which is simply not true. On the other hand, with the increases in treatment that have occurred since the 1990s, one might have hoped for a decreased prevalence, which has also not occurred.