As of January 1, 2018, claims for work-related chronic mental stress have been recognized in workplace
compensation cases in Ontario. The vast majority of these chronic mental stress claims however have
been unsuccessful given the difficult criteria required to prove these claims.
A worker is generally entitled to benefits for chronic mental stress “if an appropriately diagnosed mental
stress injury is caused by a substantial work-related stressor.” In addition, the WSIB decision maker must
be able to identify what has happened to cause chronic mental stress, including gathering information
from co-workers and supervisory staff. This process represents a significant barrier to gathering crucial
evidence for the claim given that chronic mental stress is often caused by co-workers and supervisory
staff who would likely refuse to confirm the existence of information required to proceed with a claim.
Further, workers must prove that their workplace was the “predominant cause” of chronic mental
stress. WSIB Policy 15-03-14 defines predominant cause as “the primary or main cause of the mental
stress injury – as compared to all of the other individual stressors”. Using the predominant cause test is
a very high standard that is also used in many other Provincial jurisdiction’s workplace compensation
boards such as British Columbia, Alberta, Saskatchewan and Quebec. By comparison, workers submitting
claims for physical injuries only have to show their workplace was a contributing factor to the injury.
The difficulty in proving chronic mental stress has identified a significant gap between the treatment of
physical injuries versus mental injuries. Mental injuries are still viewed as more subjective and suspect
than physical ones, often to the detriment of workers trying to advance a claim for chronic mental
stress. It is not surprising then that the WSIB has rejected the vast majority of claims related to work-
related chronic mental stress in Ontario, although the number of claims submitted remains low.
Whether the low number of claims points to a lack of education regarding these legislative changes or a
feeling amongst workers that chronic mental stress claims are likely to fail remains to be seen.