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Most employers pay premiums under Ontario’s Workplace Safety and Insurance Act, 1997 (the “WSIA”), providing workers who suffer injury or death in the course of employment with “no fault” insurance benefits.  When workplace injuries occur that are covered by WSIA benefits, workers must claim through the WSIA’s insurance plan, and are “barred” from pursuing a civil claim against their employer.

But when are mental stress claims covered?  And when must an employee claim for mental stress under the WSIA instead of filing a civil claim?

Mental Stress Coverage under the WSIA

Section 13(5) of the WSIA provides that “A worker is entitled to benefits for mental stress that is an acute reaction to a sudden and unexpected traumatic event arising out of and in the course of his or her employment.”   Because the WSIA provides that mental stress is only covered if it is “an acute reaction to a sudden and unexpected traumatic event”, many mental stress claims are not covered—at least not according to the language set out under s. 13(5).

But the WSIA’s restrictive approach to mental stress claims (as compared to its more expansive approach to claims involving a physical injury) is now under constitutional scrutiny as a result of a recent case of the Workplace Safety and Insurance Appeals Tribunal (“WSIAT”).  In this case, the Workplace Safety and Insurance Board had determined that a worker – a nurse at a hospital who had been repeatedly harassed by a physician throughout a 12 year period – was not entitled to coverage because her mental stress was not an “acute reaction to a sudden and unexpected traumatic event.”

What makes this decision so remarkable is that WSIAT found that the requirement of a “sudden and unexpected traumatic event” created a discriminatory distinction between mental disabilities and physical disabilities.  According to WSIAT, the WSIA’s distinction between mental stress claims and claims involving physical injury was arbitrary and in violation of the Canadian Charter of Rights and Freedoms (the “Charter“).  Refusing to apply s. 13(5) of the WSIA for lack of constitutionality, WSIAT concluded that the claimant was entitled to benefits, and sent the matter back to the WSIB to decide on the amount of benefits that were to be paid under the circumstances.


According to this decision, workers are entitled to broader coverage under the WSIA for mental stress—coverage that applies to mental stress that is not “an acute reaction to a sudden and unexpected traumatic event”.  However, WSIAT does not have the jurisdiction to declare a provision of the WSIA to be universally unconstitutional.  Such a binding declaration can only be made by a court of competent jurisdiction.

Practically speaking, this decision has given rise to a period of uncertainty.  When mental stress claims arise, it is now more difficult to determine whether WSIA coverage applies for cases not involving an “acute reaction to a sudden and unexpected traumatic event”.  It is therefore also difficult to determine whether an employee is “barred” from claiming damages for mental stress in the context of a civil claim.

In any event, during this period of uncertainty, we may see an increase in WSIA premiums, and we may see legislators attempt to amend the WSIA to address the constitutional issues raised by WSIAT.

Many thanks to Alex Lemoine for his assistance in drafting this article.