Examining the influence of social-environmental variables on self-injurious behaviour in adolescent boys with fragile X syndrome.

BACKGROUND: Individuals with fragile X syndrome (FXS), the most common known inherited form of intellectual disability, are at increased risk for showing specific forms of self-injurious behaviour (SIB) such as hand biting and head hitting, suggesting that biological factors associated with the syndrome confers increased risk for SIB. Few studies, however, have examined the extent to which social-environmental variables can influence the occurrence of these behaviours in this population. METHOD: Twenty-two adolescent boys with FXS, aged 10 to 18 years were systematically exposed to seven environmental conditions in functional analyses of SIB conducted over 2 days at our research centre. RESULTS: Fourteen (63.6%) boys with FXS engaged in SIB during the functional analyses. Ten (45.5%) boys engaged in SIB that was maintained by social-environmental variables, that is, gaining access to attention/tangibles and/or escaping from social interaction, task demands and/or transition demands. For two boys, SIB was undifferentiated across conditions, and for two boys, SIB appeared to be maintained by automatic reinforcement. CONCLUSIONS: Social-environmental variables appeared to maintain SIB in a significant proportion of boys with FXS. Given that pharmacological treatments for SIB have limited efficacy in this population, the potential role of social-environmental factors on SIB should be examined before pharmacological treatments are implemented for these behaviours.

Problem behaviour in adolescent boys with fragile X syndrome: relative prevalence, frequency and severity.

BACKGROUND: A large proportion of boys with fragile X syndrome (FXS), the most common known inherited form of intellectual disability (ID), exhibit problem behaviours (e.g. aggression, self-injury, property destruction and stereotypy) that can negatively impact the health and safety of others as well as the individual concerned. However, data are limited concerning the relative prevalence, frequency and severity of problem behaviours exhibited by boys with FXS compared with those by boys with mixed-aetiology ID who also exhibit problem behaviours. METHOD: As part of a larger study on problem behaviour, we obtained survey data on 85 adolescent boys with FXS and 155 age-matched boys with mixed-aetiology ID who exhibited at least one form of problem behaviour. RESULTS: For boys with FXS, stereotypy was reported to be more prevalent (χ2 = 4.52, P = 0.012), self-injury was reported to more frequent (U = 2525, P = 0.010) and aggression was reported to be less severe (U = 4176, P = 0.029) than for boys with mixed-aetiology ID. Ratings of aggression and property destruction were highly correlated in each group in terms of both frequency and severity (r = 0.60 to 0.71). Examination of the data by age indicated that the relative frequency of self-injury decreased with age in boys with FXS (χ2 = 8.29, P = 0.040). CONCLUSIONS: Taken together, these results refine and extend previous studies concerning the specificity of the behavioural phenotype in FXS and indicate that specific forms of problem behaviour shown by boys with FXS appear to differ from those exhibited by boys with mixed-aetiology ID in terms of prevalence, frequency and severity. Studies employing more objective measures of frequency and severity, including direct observations, are needed to confirm these findings.