Risk Factors for Self-Injurious Behaviors in Autism Spectrum Disorders

Background: Self-injurious behaviors (SIB), such as head banging, nail picking, self pinching, and self biting, are often highly repetitive and rhythmic and result in physical harm to the individual. These behaviors are common in autism spectrum disorders (ASD) and may be reported as early as 17 months of age. Early intervention may improve outcomes. Without intervention, SIB may become chronic, resulting in adverse consequences for the individual, the family and society. A more complete understanding of risk factors for SIB in ASD may increase opportunities for prevention.

Objectives: To assess potential associations between risk factors and parent-reported presence of SIB in a large, well-defined sample of children with ASD, and to explore whether identified relationships are modified by sex, IQ, or maternal education. 

Methods: This cross-sectional study includes 5012 children aged 2 to 17 years recruited from 2008 to 2012 at 17 sites that are part of the Autism Treatment Network registry. All included children met DSM-IV-TR criteria and also exceeded ADOS-G cut-off scores for ASD. The outcome was parent-reported presence of SIB. Risk factors examined included sociodemographics (e.g., sex, child age, maternal education, race/ethnicity); development (IQ, adaptive behaviors skills scores, developmental regression); autism severity (from calibrated ADOS-G scores); and parent-reported associated symptoms (sensory abnormalities) and behaviors (e.g., aggression, attention problems, anxiety). For two subsets of participants, parents were also asked for information on parental age (n=3017) and any gastrointestinal (GI) or sleep problems (n=4615), respectively. Site and study year were included in all analyses. We used multiple imputation to account for missing data (proportion of missing data: 0.9-21.3%) and multivariable logistic regression to test the association between SIB and the risk factors, and any modification of identified associations by sex, IQ, or maternal education.

Results: A total of 1683 children (33% of the total sample) had SIB based on parental report. SIB was significantly associated with having: a mother without a college degree (adjusted OR=1.41; 95% CI: 1.22, 1.64), public insurance (aOR=1.41; 1.15, 1.73), developmental regression (aOR=1.35; 1.16, 1.57), aggression (aOR=3.38; 2.92, 3.90), anxiety (aOR=1.47; 1.24, 1.74), hyperactivity (aOR=1.46; 1.24, 1.73), mood problems (aOR=1.74; 1.50, 2.04), and sensory abnormalities (aOR=1.48; 1.23, 1.77). SIB was negatively associated with adaptive behaviors skills scores (aOR=0.97; 0.96, 0.98) and child age (aOR=0.98; 0.92, 0.97). There was no effect modification of these associations by sex, IQ, or maternal education. In the first sub-analysis, SIB was not associated with maternal age (aOR=0.99; 0.97, 1.01) or paternal age (aOR=0.99; 0.97, 1.01). In the second sub-analysis, SIB was more likely to be reported in the presence of sleep problems (aOR= 1.44; 1.21, 1.71) but not GI problems (aOR=1.12; 0.95, 1.32). In both sub-analyses, the prediction model was similar to the main model for the rest of the variables.  

Conclusions: Diverse demographic, developmental, somatic, and behavioral characteristics associated with presence of SIB in ASD might help identify phenotypic subtypes, with implications for understanding etiology. These findings may also assist in earlier identification of children with ASD who are at risk for SIB, potentially leading to provision of appropriate interventions and better outcomes.