Autism Spectrum and Substance Use Disorder: Protective and Risk Factors

Background: The social and behavioural characteristics of individuals with Autism Spectrum Disorder (ASD) were initially presumed to protect these individuals from substance abuse. However, recent findings suggest that rates of substance use disorder (SUD) in individuals with ASD may be as high as 36%. The risk and protective factors for SUD that are unique to people with ASD, and how these factors interact to influence social adaptation and quality of life of people with ASD are not well understood.

Objectives: To review the evidence base on co-occurring ASD and SUD in order to inform clinical practice and future research.

Methods: A systematic review was conducted of identified studies pertaining to ASD and substance use using the preferred reporting items for systematic review and meta-analysis protocol (PRISMA).The focus was on study and participant characteristics (e.g., diagnostic measures, gender, age, intellectual functioning), prevalence, risk and protective factors to SUD, and consequences of SUD (i.e., impact of interaction of risk and protective factors on functional outcomes). In addition, studies were evaluated for methodological quality and risk of bias based on the Mixed Methods Appraisal Tool (MMAT).

Results: Twenty-five studies were included in the analysis. Overall study quality was high (M= 76.8%). There was wide variability in sample characteristics, and means of assessing ASD and SUD. In addition, no assessment measures designed specifically to screen for SUD in individuals with ASD were identified. Prevalence of ASD and co-occurring SUD ranged from 1.3-36%. Alcohol appears to be the most frequently used substance for individuals with ASD. The trajectories of ASD to SUD appear to differ depending on the presence of concomitant conditions, cognitive and personality factors and environmental conditions. A number of known risk and protective factors were identified, such as familial history of SUD, co-occurring internalizing (i.e., anxiety) and externalizing disorders (i.e., ADD, ODD). In addition, factors that are unique to or exacerbated in individuals with autism (e.g., limited social support, disengaging coping behaviours, low sensation seeking, late ASD diagnosis) that may serve to increase or decrease their risk of SUD were also identified. Having a diagnosis of ASD was both a risk and a protective factor for SUD but may be explained by co-occurring intellectual disability (an identified protective factor) in some samples. Substance use was associated with diminished quality of life, increased psychological distress and higher functional disability for individuals with ASD. Treatment success for individuals with ASD includes highly structured CBT focused therapy, and controlled substance use, but these have yet to be examined in an RCT study.

Conclusions:Due to variability in sample characteristics an accurate prevalence rate of SUD in individuals with ASD cannot be established at present. More research, using comparable samples and standardized measures of both SUD and ASD is needed to clarify conflicting results regarding the risk and protective aspects of having an ASD diagnosis and to establish a prevalence rate of SUD in this population. There is also a need for research on interventions that take account the special needs of this group.