Abstract
BACKGROUND: Self-injurious behaviour (SIB) is a common problem among individuals with intellectual and developmental disabilities (IDDs) with important impacts on quality of life. Although some evidence suggests that SIB may increase with age, perhaps in a curvilinear pattern, this is primarily based on cross-sectional studies. Therefore, the purpose of the current study was to conduct a prospective, longitudinal analysis of age-related changes in a high-risk cohort of children with developmental disabilities/delays. METHODS: A total of 110 participants, between 2 and 12 years of age at enrolment (70% male), were followed for between 2 and 4 years. Caregivers completed the RBS-EC SIB subscale annually, for a total of 317 assessments. The SIB total score, SIB interference ratings and endorsement of specific topographies were selected as dependent measures. Generalised linear models evaluating linear, quadratic and cubic age-related changes and differences by intellectual disability (ID) status (no or mild ID vs. moderate to profound ID) were created for each outcome. RESULTS: For SIB total scores, the model suggested complex developmental patterns that varied by degree of ID. For SIB interference ratings, the model suggested that individuals with moderate to profound ID showed relatively high and stable levels of SIB interference across ages, whereas individuals with no or mild ID showed an increasing trend with age. Patterns varied across the specific SIB topographies. DISCUSSION: The results suggest that age-related changes in SIB are complex and may vary across topographies. Overall, the results are concerning in that they indicate a potentially increasing trend in frequency of SIB and its impact on daily activities as individuals approach adolescence, indicating the need for further longitudinal work across the lifespan.