Hillery J., Dodd P.

Published: Psychiatric and Behaviour Disorders in Developmental Disabilities and Mental Retardation, United Kingdom, C.U.P., 2007, pp225 - 238,

Self-mutilation has been recorded through history, across cultures, and can be culturally congruent (Favazza, 1989). Self-mutilation is the deliberate alteration or destruction of body tissue without conscious suicidal intent. It can be seen as a symptom of psychiatric disorder or as a distinct syndrome. Favazza and Rosenthal (1993) have suggested that it be classified into three basic types, major, superficial and stereotypic. In this classification, major self mutilation is associated with acute psychiatric illness or severe personality disorder. Superficial self-mutilation is a common behaviour (from 400 to 1400 per 100,000 of population per year) that is a symptom or associated feature of many psychiatric disorders. Stereotypic self-mutilation is most commonly seen in institutionalised people with developmental disabilities, although Favazza admits that not all self-mutilation in people with developmental disabilities is of this type. Indeed, we know that people with developmental disabilities can show myriad forms of self-mutilation. This behaviour is referred to as self-injurious behaviour in people with developmental disabilities. It can be resistant to treatment, has no apparent cause, and can be responsible for much medical, psychological and social morbidity.

The definition of self-injurious behaviour varies from author to author, this variety has made comparison between epidemiological studies difficult. The definitions used generally include the requirement that the actions cause damage to the self. This tissue damage criterion (Oliver, Murphy & Corbett, 1987) also allows for the fact that people may be wearing protective clothing (e.g. a helmet) by including actions that would cause tissue damage if the person were not wearing such clothing. Oliver et al. (1987) reported that the ‘tissue damage’ criterion proved robust when judging the ability of different informants to agree on caseness.


Self-injurious behaviour is a common reason for people with developmental disabilities being excluded from community-based educational services and vocational training (Shlalock et al, 1985). Those in residential care who self-injure are probably less likely to receive a day service than those who do not (Oliver et al, 1987). The conclusion from available research is that exhibiting self-injurious behaviour considerably decreases a person’s quality of life.


Epidemiology
Comparing epidemiological studies of self-injurious behaviour, one finds widely varying prevalence rates. This is due to differences in the methodology of the studies, the definition used and the populations studied. The last-mentioned have varied in age, level of intellectual ability, type of disability (i.e. single or multiple disability) and in their origin (i.e. geographically based or service based).

Prevalence rates as low as 1.7 percent (Rojahn, 1986) and as high as 41 percent (Saloviita, 1988) have been reported. Studies that take place in residential services produce higher prevalence rates than community studies. This is because people who self-injure are more likely to be in residential care. Even with the effort to correct for bias by using geographically based populations (Kebbon & Windahl, 1985, 4.2 per cent; Hillery & Mulcahy, 1997, 14 per cent; Collacott et al., 1997, 16 per cent, there is still a wide variation in prevalence. Rojahn (1994) points out that studies based on service system databases are biased in favour of those who proclaim an urgent need for service and against those who do not take up services, for whatever reason.

It seems apparent from the results given above that for future epidemiological studies to be useful for furthering international approaches to self injurious behaviour, consensus must occur on parameters for choosing populations for study.

Studies of self-injurious behaviour have generally found an inverse relationship between IQ and the likelihood of a person displaying such behaviour. Although studies suggest a relationship between self-injurious behaviour and age, the relationship is not a statistically significant one.