Can Ontario Employers Get WSIB Cost Relief for Prior Conditions?

Can an employer reduce WSIB claim costs because of a worker’s pre-existing condition?

Sometimes, but only when the evidence shows the earlier condition played a significant role in the workplace injury or in the worker’s recovery. The WSIB’s Second Injury and Enhancement Fund (SIEF) policy allows an employer’s claim costs to be reduced in limited situations.

As explained in Decision No. 796/26, 2026 ONWSIAT 1040 (CanLII), Policy 14-05-03 allows relief where a pre-existing physical or psychological condition caused or contributed to the compensable accident, or where it enhanced or prolonged the worker’s compensable injury or disability.

The policy separates two kinds of earlier problems. A pre-accident disability is one that caused past periods of disability, needed treatment and interrupted work. A pre-existing condition is an underlying or silent condition that only shows itself after the accident.

The Tribunal applied a significant contribution test. The earlier condition must be a factor of considerable effect or importance, though it does not need to be the only one, and it must be proven on a balance of probabilities.

What happened in this Ontario PTSD case?

The Workplace Safety and Insurance Appeals Tribunal (WSIAT) refused an employer’s request for SIEF cost relief on a registered practical nurse’s PTSD claim. The nurse had worked at a psychiatric hospital since 2004.

The WSIB accepted the PTSD claim under its policy for first responders and other designated workers, with a date of injury of December 11, 2017. The worker later reached maximum medical recovery and received a 20% non-economic loss (NEL) award. According to the record, he was permanently restricted from direct care and from work with a high risk of violence or trauma.

In 2024, the employer asked for SIEF relief. The WSIB denied the request, and an Appeals Resolution Officer upheld that denial in March 2025. The employer appealed to the Tribunal, which decided the matter in writing. The worker did not participate, and the only issue was whether the employer qualified for SIEF relief on the costs of the claim.

Does a past concussion or depression automatically qualify an employer for SIEF relief?

No. The Tribunal found the worker did have earlier concussion and psychological conditions, but the evidence did not show they prolonged or enhanced the PTSD disability.

In 2011, a patient struck the worker in the head. Brain imaging came back normal. A 2012 psychiatric assessment found an adjustment disorder with depressed mood that had resolved, along with probable ADHD, and said no treatment was needed. A neuropsychologist found nothing compelling to show lasting effects from the mild brain injury and placed no restrictions on a return to work.

The worker returned to regular duties in late 2012, and the WSIB found in 2013 that he had fully recovered. The Vice-Chair found no records of concussion or psychological complaints after 2012. Even after a February 2017 incident in which a patient strangled him with his helmet strap, there was no medical documentation of psychological symptoms until the PTSD diagnosis in December 2017.

Later specialists who knew about the earlier injuries did not say those injuries prolonged recovery from the PTSD. One psychiatrist said the worker’s ADD was not a significant source of his impairment.

Can vulnerability or family history support a SIEF claim for PTSD?

Only with real evidence about the particular worker. General risk factors and unsupported assertions were not enough in this case.

The employer argued that concussions raise the risk of later psychiatric conditions, that the worker had a family history of bipolar disorder and depression, and that a past breakup or other life experiences may have caused earlier psychic trauma. The Vice-Chair acknowledged that the policy says possible prior psychic trauma from life experience could be treated as evidence of vulnerability, even without an earlier psychological impairment.

However, the Vice-Chair stressed that it is not enough for a condition to predispose a worker to injury. There must be medical evidence that the condition prolonged or enhanced recovery. The Tribunal’s medical discussion paper states that concussion nearly triples the risk of a later psychiatric condition, and the Vice-Chair accepted that general risk. Still, there was no evidence that this worker’s concussion led to a psychiatric condition.

The family history and breakup points were described as unsupported assertions with no evidence from which reasonable inferences could be drawn. Citing earlier Tribunal decisions, the Vice-Chair noted that speculative arguments about pre-existing conditions generally do not succeed without medical support.

When has the WSIAT granted SIEF relief?

The decision pointed to an earlier case where relief was granted because a medical opinion directly linked a pre-existing condition to the injury and the time off work.

The employer relied on Decision No. 2970/18, which involved a knee strain in a worker with pre-existing knee arthritis. The knee was not symptomatic right before the injury, but a medical opinion said the arthritis affected both the extent of the injury and how long the worker was off. The employer in that case received 90% relief.

The Vice-Chair found this case different because no medical opinion said the worker’s earlier conditions prolonged or enhanced his recovery. Given that finding, the Tribunal did not need to consider how severe the workplace accident was.

Why does this decision matter to Ontario workplaces?

It shows that, in this Tribunal’s analysis, SIEF relief depended on medical evidence specific to the worker rather than on the mere existence of a past diagnosis.

The worker’s history included a prior workplace head injury, a resolved mood condition and an ADD diagnosis. Each was documented, yet none was linked by a medical opinion to a longer or worse PTSD disability. The record of full recovery, a return to regular duties and years without symptoms carried significant weight.

Questions and records to discuss with a lawyer

• Medical records showing whether an earlier injury or condition fully resolved, and when
• Return-to-work and regular-duties history between an earlier injury and a later claim
• Specialist or assessment reports that comment on whether a prior condition affected recovery
• WSIB decision letters, including any finding of full recovery or any NEL award
• How the WSIB or Appeals Resolution Officer decision under appeal framed the issue

Workplace injury claims and the cost disputes that follow them can raise detailed questions about medical evidence and WSIB policy. If you would like advice about your own circumstances, our Ontario employment lawyers, including our Toronto employment lawyers, are available. You can contact UL Lawyers through our connect page.

---

This article is automated commentary on a public court decision and is for general information only — not legal advice. Decisions rely on facts unique to each case. If you are affected by a similar issue, contact a lawyer for advice specific to your situation.