Wednesday, February 9, 2011

Bell's "Let's Talk Day": Right Idea - Wrong Estimates: Are Health Organizations in Canada Underestimating the Prevalence of Mental Illness?

Bell Canada is promoting mental health awareness today with their "Let's Talk Day." It's a great idea that will see Bell contribute 5 cents from every text and long distance call to support mental health programs. I also love Clara Hughes' involvement in the project - an act that is both courageous and generous.

However, I am quite certain that Bell has its "1 in 5 Canadians" figure wrong. You may have seen the advertisements on TV or the web where Bell cites a figure from the Canadian Institute of Health Research (CIHR) which states that 1 in 5 Canadians will experience mental illness in their lifetime. You will find a similar figure on both the Health Canada and Canadian Mental Health Association (CMHA) websites. Unfortunately, I suspect they are all incorrectly citing data from one study(1).



On the CMHA website (the Fast Facts section, see here), they cite the 1 in 5 (or 20%) figure and offer as a reference The Report on Mental Illness in Canada (see report here). This report is from 2002 and does not state that 1 in 5 Canadians will be affected by mental illness in their lifetime. The actual statistic used is 1-year prevalence, not lifetime prevalence. This estimate comes from regional studies of prevalence (Ontario and Edmonton), which presumably has been extrapolated to Canada.

So, what is the actual lifetime prevalence of mental illness in Canada? The Report on Mental Illness in Canada notes that such data should be forthcoming from Canada's Canadian Community Health Survey (CCHS). However, when I tried to find results from this research group on national prevalence, I couldn't find anything, so I don't think the data are yet available.

However, we can look to U.S. estimates of prevalence to get a sense of what the numbers in Canada would look like. Arguably the best research study on prevalence in the U.S. comes from the National Comorbidity Survey - Replication(2). In this report, 12 month prevalence of mental illness is approximately 26%, and is closer to the Canadian figure that is incorrectly used as lifetime prevalence. The lifetime prevalence of mental illness in the U.S. is 46%, which gives a rough Canadian estimate (I suspect the Canadian Community Health Survey will have comparable outcomes).

Thus, it is not the case that 1 in 5 Canadians will be affected by mental illness - the real number is likely much higher - closer to 2 in 5 Canadians.

UPDATE I

I've contacted CMHA, Health Canada and even Bell Canada to inform them of the apparent error. I was told by all that they'd get back to me. It's been about a week.

UPDATE II

I received a detailed response from a representative of the Public Health Agency of Canada. See here for details.

References

(1) Offord DR, Boyle MH, Campbell D, Goering P, Lin E, Wong M, Racine YA. One-year prevalence of psychiatric disorder in Ontarians 15 to 64 years of age. Can J Psychiatry 1996;41:559-563

(2) Kessler et al. (2005). Lifetime Prevalence and Age-of-Onset Distributions
of DSM-IV Disorders in the National Comorbidity Survey Replication. Archives of General Psychiatry, 62, 593-602.

No comments: