Assessing Permanent Impairment Due to Mental and Behavioural Disorders


Workers who have a permanent impairment due to a work-related mental or behavioural disorder are entitled to non-economic loss (NEL) benefits based on the severity of the impairment.


Rating impairment

The WSIB attempts to determine the degree of the worker's permanent impairment by considering all relevant health care information in the claim file.

If the existing health care information in the claim file is insufficient to determine the degree of the worker's permanent impairment, the WSIB requests additional health care information from the worker or the worker's physician(s). If the information is still insufficient, the WSIB requires the worker to attend a NEL medical assessment conducted by a roster physician, see 18-05-03, Determining the Degree of Permanent Impairment, to determine the condition of a mentally or behaviourally impaired worker.

The WSIB then rates the condition using the Mental and Behavioural Disorders Rating Scale, which combines elements of the American Medical Association's Guides to the Evaluation of Permanent Impairment, 3rd edition (revised), (the AMA Guides) with the WSIB's Psychotraumatic and Behavioural Disorders Rating Schedule.

Mental and Behavioural Disorders Rating Scale

The following scale applies to the assessment of permanent impairment benefits for psychotraumatic disability, chronic pain disability, and fibromyalgia syndrome.

Class 1, No impairment (0%) - no impairment noted

Class 2, Mild impairment (5-15%) - impairment levels compatible with most useful function

There is a degree of impairment of complex integrated cerebral functions, but the worker remains able to carry out most activities of daily living as well as before. There is also some loss in personal or social efficacy and the secondary psychogenic aggravations are caused by the emotional impact of the accident.

There is mild to moderate emotional disturbance under ordinary stress. A mild anxiety reaction may be apparent. The display of symptoms indicates a form of restlessness, some degree of subjective uneasiness, and tension caused by anxiety. There are subjective limitations in functioning as a result of the emotional impact of the accident.

Class 3, Moderate impairment (20-45%) - impairment levels compatible with some but not all useful function

There is a degree of impairment to complex integrated cerebral functions such that daily activities need some supervision and/or direction. There is also a mild to moderate emotional disturbance under stress.

In the lower range of impairment the worker is still capable of looking after personal needs in the home environment, but with time, confidence diminishes and the worker becomes more dependent on family members in all activities. The worker demonstrates a mild, episodic anxiety state, agitation with excessive fear of re-injury, and nurturing of strong passive dependency tendencies.

The emotional state may be compounded by objective physical discomfort with persistent pain, signs of emotional withdrawal, depressive features, loss of appetite, insomnia, chronic fatigue, mild noise intolerance, mild psychomotor retardation, and definite limitations in social and personal adjustment within the family. At this stage, there is clear indication of psychological regression.

In the higher range of impairment, the worker displays a moderate anxiety state, definite deterioration in family adjustment, incipient breakdown of social integration, and longer episodes of depression. The worker tends to withdraw from the family, develops severe noise intolerance, and a significantly diminished stress tolerance. A phobic pattern or conversion reaction will surface with some bizarre behaviour, tendency to avoid anxiety-creating situations, with everyday activities restricted to such an extent that the worker may be homebound or even roombound at frequent intervals.

Class 4, Marked impairment (50 - 90%) - impairment levels significantly impede useful function

There is a degree of impairment of complex integrated cerebral functions that limits daily activities to directed care under confinement at home or in other domiciles. The worker clearly displays chronic limitation of adaptation and function, in the home and outside environment, that ranges from moderate to severe. The worker is withdrawn, forgetful, unable to concentrate, and needs continuous emotional support within the family setting. The worker is incapable of self-care and neglects personal hygiene.

There is a moderate to severe emotional disturbance under ordinary to minimal stress, which requires sheltering. There may be an obvious loss of interest in the environment with the worker becoming extremely irritable, showing significant emotional liability, changes of mood, and uncontrolled outbursts of temper. The worker may be severely depressed, with outstanding features of psychomotor retardation and psychological regression.

Class 5, Extreme impairment (95%) - impairment levels preclude useful function

There is such a degree of impairment of complex integrated cerebral functions that the worker is unable to care for himself or herself in any situation or manner. There is severe emotional disturbance that continually endangers the worker or others.

Application date

This policy applies to all decisions made on or after January 1, 1998, for accidents on or after January 2, 1990.

This policy is used in conjunction with Chapter 14 of the AMA Guides, Mental and Behavioural Disorders.

Document History

This document replaces 18-05-11 dated October 12, 2004.

This document was previously published as:
18-05-11 dated June 15,1999
6.9 dated January 1, 1998.


Legislative Authority

Workplace Safety and Insurance Act, 1997, as amended
Sections 46, 47, 106

O. Reg. 175/98
Section 18

Workers' Compensation Act, R.S.O. 1990, as amended
Section 42(1), (5)

R.R.O. 1990, Reg. 1102
Section 15


Board of Directors  #1, September 7, 1990, Page 5388  
#1, February 11, 1991, Page 5427  
#1, March 1, 1991, Page 5433  

#8, May 26, 2008, Page 461