Substance Use Disorders in Autism Revisited

Autism is a heritable neurodevelopmental disorder that is approximately 4 times more prevalent in males than females.

Anywhere between 19% and 30% of individuals diagnosed with autism, a heritable, neurodevelopmental disorder that affects approximately 1 in 100 children, present with comorbid substance use-related problems. It has been proposed that one of the risk factors for substance abuse among this population is the diagnosis of attention deficit hyperactivity disorder (ADHD), which frequently co-occurs with autism spectrum disorder.

In a recent report, published in Journal of Autism and Developmental Disorders, Swedish investigators noted that a diagnosis of autism spectrum disorder is associated with a doubled risk for a variety of substance use-related problems including drug and alcohol use disorders.

In this large population-based cohort study, the researchers identified nearly 30 000 probands with an autism spectrum diagnosis, and they compared them with over 1.3 million non-autism spectrum disorder individuals. The two groups of individuals were matched by sex, birth year, and county of birth. The percentage of patients with a diagnosed, pre-existing substance use disorder was significantly higher among the persons with autism diagnosis (n=913; 3.4%) compared with that of typical, healthy controls (n=10 789; 0.8%).

The investigators used parental age, region of birth, education, and family income as covariates. In comparison to their population controls, autism spectrum disorder probands had a substantially increased risk with regard to the risk of any substance-related problem (OR 3.3; 95% CI 3.1-3.6), including substance use disorder (OR 5.2; 95% CI 4.9-5.6), somatic disease linked to alcohol misuse (OR 5.9; 95% CI 2.7-13.0), and substance-related crime (OR 1.4; 95% CI 1.2-1.5) or death (OR 3.0; 95% CI 1.3-6.9).

With regard to risk estimates for specific substance use disorder categories, the highest risk was reported for drug use disorder (OR 8.5; 95% CI 7.7-9.3), tobacco-related disorder (OR 6.4; 95% CI 3.8-10.5), and alcohol use disorder (OR 4.0; 95% CI 3.7-4.4).

“The family data suggested that [the increased risk for a range of substance use-related problems among individuals with autism spectrum disorder] was due to shared liability between autism spectrum disorder and substance use-related problems between relatives,” the authors wrote in their publication.

Since autism spectrum disorder frequently co-occurs with ADHD and intellectual disability, the investigators stratified their analyses by autism comorbidity, including ADHD and/or intellectual disability. The risk of substance-use related problems was substantially higher among those with comorbid ADHD (OR 8.3; 95% CI 7.4-9.2), followed by comorbid ADHD with intellectual disability (OR 4.6; 95% CI 3.7-5.8).

“Our finding of a mediating role of familial risk factors suggest that attempts to prevent or treat substance use disorder in autism spectrum disorder probands should consider also the vulnerabilities of other first degree family members,” the authors concluded.

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Butwicka A, Långström N, Larsson H, et al. Increased risk for substance use-related problems in autism spectrum disorders: a population-based cohort study. J Autism Dev Disord. 2016. DOI: 10.1007/s10803-016-2914-2.