Self injurious behaviour directly results in some physical harm to an individual, or is where people display repetitive movements even though these may not immediately produce tissue damage.

There is a hypothesis that in some cases of chronic self-injurious behaviour, the individuals involved may have altered or diminished pain perception.

The researchers in this study set out to test this idea by looking at how often people diagnosed with a learning disability engaging in chronic self-injury displayed non-verbal signs of pain in relation to their self-injury.

They worked with four people, aged between 28 and 50, and videotaped them in their homes during times when they were likely to engage in self-injury.

They used continuous recording measures to code the tapes for frequency and duration of self-injury and any expressions of non-verbal pain-related behaviours.

What they found was that existing measures of pain could be systematically related to instances of self-injury. They did find though that the relationships might vary depending on the person engaging in the self-injury, the contexts in which it occurs (for example the environment) and also the type of self-injury in which the person engages.

Whilst the study is very small in terms of the numbers of participants, the researchers suggest that their findings raise a number of questions about the idea that people with chronic self injury may have altered or diminished pain perception – the so called blunted nociception hypothesis of self-injury.

Observing signs of pain in relation to self-injurious behaviour among individuals with intellectual and developmental disabilities, Courtemanche, A et al., in Journal of Intellectual Disability Research, 56: 501–515