Administrative practice document: Traumatic mental stress (TMS)

Note: This is not a policy. It is a supplementary document to illustrate how the WSIB will administer the Workplace Safety and Insurance Act, 1997, (WSIA) and Policy 15-03-02, Traumatic Mental Stress in practice. If there is a conflict between this Administrative Practice Document and the WSIA and/or WSIB policy, the decision-maker will rely on the WSIA and/or WSIB policy, as the case may be.

Key principles

  • Adjudication is the process used to determine entitlement to benefits and services under the WSIA.
  • A decision-maker is the person who makes decisions about entitlement.
  • Decision-makers will gather relevant information and weigh evidence to make decisions about entitlement.
  • Workers are entitled to receive benefits for injuries and illnesses that result from incidents that arise out of and in the course of employment.
  • Work-relatedness is established when determining initial entitlement. Decision-makers continue to evaluate the work-relatedness of a worker’s ongoing impairment and treatment throughout the life of a claim.
  • The WSIB makes its decisions based on the merits and justice of each case.
  • When the evidence for and against an issue relating to a worker’s claim are equal, we give the worker the benefit of doubt.


Decision-makers at the WSIB must decide a worker’s entitlement to benefits and services under the WSIA. For entitlement to exist, the worker’s injury must be the result of an incident that arose out of and in the course of employment, or that the worker suffers from an occupational disease that occurred due to the nature of employment.

In addition, s.13(4) of WSIA states:

A worker is entitled to benefits under the insurance plan for chronic or traumatic mental stress arising out of and in the course of the worker’s employment. 2017, c. 8, Sched. 33, s. 1.

S. 13 (5) of WSIA states:

A worker is not entitled to benefits for mental stress caused by decisions or actions of the worker’s employer relating to the worker’s employment, including a decision to change the work to be performed or the working conditions, to discipline the worker or to terminate the employment. 2017, c. 8, Sched. 33, s. 1.

This document outlines the approach for dealing with several of the more challenging issues faced by decision-makers when determining entitlement for traumatic mental stress (TMS). Decision-makers are guided by s.13 (5) of the WSIA and Policy 15-03-02, Traumatic Mental Stress. A claim for TMS is different from a claim for chronic mental stress.

Note: Policy 15-03-14 Chronic Mental Stress guides entitlement decisions for mental stress injuries arising from a substantial work-related stressor that is not considered objectively traumatic.

Note: Policy 15-04-02, Psychotraumatic Disability guides entitlement decisions for psychological conditions that become evident secondary to a work-related physical injury.

Note: Policy 15-03-13, Posttraumatic Stress Disorder in First Responders and Other Designated Workers (Legislative reference Bill 163, Supporting Ontario’s First Responders Act, 2016) guides entitlement decisions for first responders or other designated workers diagnosed with posttraumatic stress disorder (PTSD). This document does not relate to the application of Policy 15-03-13. Where the criteria in Policy 15-03-13 are not met, entitlement may be considered under the TMS policy.

Collecting relevant evidence

When gathering the evidence in a traumatic mental stress (TMS) claim, direct contact with the worker is essential in understanding the worker’s view of the workplace event(s), any personal events, and the onset and details of the worker’s symptoms. Decision-makers use sensitive questioning and active listening as the worker’s medical status may be fragile.

Decision-makers must gather all relevant and available information to assess and weigh the evidence to determine a worker’s entitlement to benefits and services under the WSIA. Where possible, decision-makers gather information by phone and obtain medical reports from the health care professionals involved in the worker’s case. Decision-makers must make all reasonable attempts to obtain any missing information to ensure the relevant information is available for consideration throughout the adjudicative process. Working with a claims investigator is advisable in these cases, especially if the decision-maker needs several statements from the employer, co-workers or other individuals.

In some instances, initial inquiries may reveal other potential factors may have contributed to the onset of the condition. These factors may include non-work-related stressors and/or traumatic events, stressors resulting from the employer’s employment decisions or actions, or a pre-existing psychological condition. Decision-makers must gather information related to other stressors and the associated medical history, as it is relevant to determining the work-relatedness of the onset of the worker’s psychological condition.

Information is relevant to the claim when it has value in weighing the evidence to establish a matter of fact in a case, i.e. it has a bearing on the decision-making process. Relevancy does not speak to the weight given to the information in the decision-making process. Decision-makers consider and weigh all relevant information to reach a decision. When determining entitlement for TMS, decision-makers must assess and weigh each piece of evidence to determine whether the worker’s psychological condition is work-related, particularly in cases where there is a delayed onset of the condition or seeking of medical attention.

In complex situations, a case conference with the nurse consultant and/or manager may assist the decision-maker’s assessment of the evidence. In complex cases of causation and compatibility, decision-makers may request the opinion of a Psychiatric Medical Consultant. In some cases, the decision-maker may determine an assessment by an external expert is necessary to provide an additional opinion.

It is important to note a worker is not entitled to benefits for TMS resulting from the employer's employment decisions or actions.

Determining a traumatic event

A worker must experience an identifiable and objectively traumatic event to be considered for TMS entitlement. A traumatic event may be a result of a criminal act, harassment, or a horrific accident, and may involve actual or threatened death or serious harm against the worker, a co-worker, a worker’s family member, or others. In most cases, a traumatic event will be sudden and unexpected; however this is not a requirement for the purposes of determining entitlement.

In all cases, the event must arise out of and occur in the course of the employment, and be

  • clearly and precisely identifiable, and objectively traumatic - independent of the person’s perspective, would any reasonable person recognize the event as traumatic?

In addition to information from the worker, decision-makers may obtain information from co-workers, supervisory staff, or others. It can be accepted that a traumatic event occurred when co-workers, supervisory staff, or other individuals have direct knowledge of the event, and the event is generally considered traumatic in nature.

Traumatic events include, but are not limited to:

  • witnessing a fatality or a horrific accident
  • witnessing or being the object of an armed robbery
  • witnessing or being the object of a hostage-taking
  • being the object of physical violence
  • being the object of death threats
  • being the object of threats of physical violence where the worker believes the threats are serious and harmful to self or others (e.g., bomb threats or confronted with a weapon)
  • being the object of workplace harassment including physical violence or threats of physical violence (e.g., the escalation of verbal abuse into traumatic physical abuse)
  • being the object of workplace harassment including being placed in a life-threatening or potentially life-threatening situation (e.g., tampering with safety equipment; causing the worker to do something dangerous)

The worker must have suffered or witnessed the traumatic event first-hand, or heard the traumatic event first-hand through direct contact with the traumatized individual(s) (e.g., speaking with the victim(s) on the radio or telephone as the traumatic event is occurring).

Cumulative effect

Some workers may be exposed to multiple traumatic events over time, due to the nature of their occupation. If a worker experiences traumatic mental stress (TMS) because of the most recent traumatic event, entitlement may be in order even if the worker was able to tolerate the past traumatic events. A final reaction to a series of traumatic events is considered to be the cumulative effect.

In some cases, there may have been multiple traumatic events, none of which resulted in lost time from work or the need for medical attention. Despite having had more serious traumatic events take place before, an event considered minor in comparison may trigger an emotional response. The decision-maker must carefully investigate whether it is the cumulative effect of each of these events that has caused the reaction after the most recent event.

Other traumatic events

The list of examples set out in policy as traumatic events generally characterize the types of events decision-makers would consider for entitlement to TMS. There may be other types of events not included in this list, which would reasonably align to the events described.

The involvement by an individual in an event that poses imminent danger but does not, in the end, result in a tragic outcome; can be considered a traumatic event. This may be a circumstance where a worker believes their life is in imminent danger, only to find out this is not the case, as the situation plays out. This “close call” event may be traumatic from the worker’s perspective. If the decision-maker accepts this was objectively traumatic, there may be entitlement should the worker develop a reaction to the event. To make an entitlement decision, the decision-maker must complete a thorough review of the circumstances surrounding the event.

Decision-makers should consider the following questions:

  • What was the potential impact of the event? Could it have resulted in serious injury or death to the worker or to others?
  • Were there previous related incidents that might add objective strength to the concern/reaction of the worker to the event?
  • Was timely medical attention sought, and is the description provided to the treating health care practitioner consistent with the facts as known?

Workplace harassment interactions that include physical violence, threats or being placed in potentially life-threatening situations within the work environment may also support entitlement for TMS. Decision-makers should consider:

  • Were the actions of the supervisor or co-worker considered threatening?
  • Is the worker’s version of events credible? Is it corroborated by others?
  • Was there an immediate and obvious impact demonstrated by the physical reaction and the immediacy of the diagnosis?
  • Would any reasonable person recognize this occurrence as traumatic?
  • Is the supervisor’s behavior/approach consistent with action that would be considered “not part of the employment function” as noted in the policy?

Diagnostic requirements

Before any traumatic mental stress can be adjudicated, there must be a diagnosis in accordance with the Diagnostic and Statistical Manual of Mental Disorders (DSM).

In most cases, the WSIB will accept the claim for adjudication if an appropriate regulated health care professional provides the DSM diagnosis. In complex cases, however, if there is evidence a non-work related stressor(s) may cause or contribute to the injury, the WSIB decision-maker may require a further assessment, including an assessment by a psychiatrist or psychologist, to help clarify initial or ongoing entitlement.

Pursuant to the Regulated Health Professions Act, 1991, regulated health care professionals who are qualified to provide a DSM diagnosis are:

  • physicians,
  • nurse practitioners,
  • psychologists, and
  • psychiatrists.

The following are the diagnoses most commonly seen in traumatic mental stress claims.

Acute stress disorder (ASD) is an anxiety condition that develops within days after a severe traumatic event or experience and does not persist beyond four weeks. The nature of the acute reaction can be variable, but generally would be described in terms of apprehension, anxiety, insomnia, poor concentration, unwanted recollections of the event, guilt or anger.

The following are the diagnoses most commonly seen in traumatic mental stress claims. Several of the following ASD symptoms may develop during or after the event or experience:

  • loss of emotion
  • feeling numb and detached
  • diminished awareness of surroundings
  • dissociate amnesia

It is important to review the presenting medical information to determine the extent of detail provided around the severity and duration of the symptoms when evaluating such cases. Sometimes, the initial treating physician may not have recorded all the particulars or used formal conventional DSM terminology. The formal DSM identifier may be indicated by descriptors such as “traumatic reaction”, “overwhelming stressors”, or “traumatic accident”.

Where there is an incomplete diagnosis, it is not unreasonable to accept the medical information as provided and then carefully look at the time between the event and the onset when assessing the ‘work link’ in these acute onset cases. Where there is a close proximity between the event and the onset, this lends support that the work event was the causal factor and diminishes the likelihood of the impact of other potential intervening factors.

Posttraumatic stress disorder (PTSD) is an anxiety condition that develops after exposure to a traumatic event and where the symptoms last for more than four weeks. Symptoms typically begin within three months of a traumatic event, although occasionally they do not begin until sometime later. The symptoms are essentially the same as ASD, the difference being the timing of when they appear.

Physicians often treat the symptoms without immediately associating them with PTSD. Other issues, including depression, are not uncommon in a worker suffering with PTSD. Other associated symptoms include:

  • distressing recollections of the event or experience
  • dreams that are reoccurring and distressful
  • reliving the event or experience in the form of flashbacks, hallucinations, images, illusions or thoughts
  • avoidance of similar stimuli that provoke memories of the event

These cases sometimes appear to have a “delayed onset,” noting the worker may not immediately seek medical attention, even if they have an acute reaction. The worker may have been told or be aware that most of these conditions resolve within days to weeks. Therefore, the worker may initiate a medical assessment and/or treatment only after a period of prolonged or worsening symptoms. The delay may also be due to a lack of access to immediate resources such as a physician or counsellor. Often, personal factors such as personality, history of coping with stressors, expectations from others and possibly the work environment, motivate workers to attempt to manage the events on their own, thereby delaying the seeking of assistance.

Occasionally, a delay in seeking treatment may occur when there was an initial resolution of the symptoms following the traumatic event, and then another event brings back the symptoms experienced from the initial event. The second event may be similar, or at times, quite dissimilar to the initial event, but it holds something in common with the original traumatic event, such as the experience of anxiety, horror or fear.

When assessing entitlement in cases where there is a delay in either the onset, or the seeking of medical attention, the decision-maker must fully obtain all the details surrounding the circumstances/symptoms of the traumatic event. It should be recognized in some cases, the association between the symptoms and the event may not be readily apparent to the worker or the physician. In situations where there is a delay in seeking medical attention, decision-makers should pay careful attention to the reasons provided by the worker. The symptoms experienced by a worker are unique to each person, and at times may not be immediately identified or linked to the event. A full investigation of the sequence of events following the initial event will assist in confirming whether the delay was reasonable. Decision-makers must assess and weigh all the available evidence to determine entitlement. Where the evidence supports the work event as being linked and/or related to the onset and/or development of the Axis I Diagnosis in accordance with the DSM, entitlement should be supported.

Communication of decisions

Decision-makers must communicate all adjudicative decisions verbally to the workplace parties, wherever possible, and then confirm the decisions in writing. The decision letter should

  • identify the issue decided,
  • provide a summary of the facts of the case,
  • provide the entitlement rules that apply to the issue (legislative and/or policy criteria, or standards),
  • provide the rationale for the decision reached, explaining how the entitlement rules were or were not met,
  • reference only evidence that is relevant to the decision, and
  • include the timeframe for appealing the decision for all adverse decisions.

Decision-makers make every effort to communicate decisions in plain language to ensure both the worker and the employer fully understand the decision and reasons for the decision. The rationale should outline the evidence that was considered relevant to decision-making on the identified issue.

In TMS entitlement decisions, the rationale should explain the decision-makers determination on how the legislative and policy criteria were or were not met. Where the decision-maker has weighed the significance of conflicting or differing information, the decision letter should include an explanation of the assessment of the relative weight of the evidence. The explanation should indicate whether the evidence was accepted or not, and the reasons the evidence was given more or less weight.

Where the decision-maker determines the worker has entitlement for TMS, the decision letter should indicate the accepted diagnosis, the treatment approved and the benefits payable.


When determining entitlement for TMS, direct contact with the worker is critical as it is essential to understand the worker’s view of the event and how it links to his or her psychological condition. Decision-makers must also gather the relevant and available information from the workplace parties and others, as appropriate, as well as the health care professionals involved in the worker’s treatment.
Once the decision-makers has obtained all of the critical and relevant information, they must assess and weigh the evidence to determine entitlement as guided by Policy 15-03-02, Traumatic Mental Stress and the information provided in this document.

Document history:

May 2022 – revised to reflect S.13(5) amendment.

June 2016 – revised to add references to new policy, 15-03-13, Posttraumatic Stress Disorder in First Responders and Other Designated Workers, dated April 7, 2016

March 2015 – replaces the Best Approaches Guide on Traumatic Mental Stress, 2007

Scheduled review: May 2027