Self-injurious behaviour

What is the prevalence of self-injurious behaviour in Smith-Magenis syndrome?

The prevalence of self-injury in Smith-Magenis syndrome ranges between 67-96%. These estimates are very high compared to estimates of prevalence in individuals with other genetic syndromes and intellectual disability, with individuals with Smith-Magenis syndrome at least six times more likely to show self-injury.

What forms of self-injury are common in Smith-Magenis syndrome?

It is important to remember that the types of self-injury shown by individuals with Smith-Magenis syndrome will vary, with each individual having their own repertoire of behaviours.  However, research has shown that there are some types of self-injury that are more common amongst people with Smith-Magenis syndrome, and may be of significance to the syndrome. In particular pulling out finger and toenails (onychotillomania) and insertion of objects into bodily orifices (polyembolokoilamania) seem to be highly associated with Smith-Magenis syndrome.

Self-hitting and self-biting (mainly of the hands) have been found to be the most common forms of self-injury in individuals with Smith-Magenis syndrome, with estimates of prevalence for self-hitting ranging from 71-93% and for self-biting 77-80%.

In 2011, Dr Kate Arron and her team compared the prevalence of a range of self-injurious behaviours amongst a selection of syndromes and a control group of individuals with intellectual disability of heterogeneous cause (i.e. not due to a genetic syndrome).

Download the paper here.

Research has also shown that the number of types of self-injurious behaviours shown by individuals with Smith-Magenis syndrome may increase with age, but on average an individual will show 4 different types of self-injury.

What causes self-injurious behaviour in Smith-Magenis syndrome?

Sloneem and colleagues established that self-injury in Smith-Magenis syndrome likely serves social communicative functions, such as obtaining social interaction with another person, escaping from demands or accessing a preferred item. Self-injury may also function to provide sensory stimulation for an individual, or may be associated with pain and/or discomfort.

There is some evidence that individuals who have Smith-Magenis syndrome might have peripheral sensory neuropathy.  This disorder can have two important effects that might be relevant to self-injury. First, pain may not be experienced in the ‘normal’ way.  Painful stimuli may not be experienced as painful.  Secondly, people may experience unusual sensations in their hands and arms.  These sensations are described by some people as pins and needles (dysaesthesia) or a mild burning sensation.  If this is the case, then individuals may respond to this sensation by scratching, picking or biting the area in which the tingling is occurring.  When this happens in the absence of any pain, this behaviour may become more severe than it would if the person was able to identify the pain sensation.

Download:  Example 1 – Behaviours that challenge and pain

Download: Example 2 – Behaviours that challenge and pain