Treatment seeking adults with autism or ADHD and co-morbid substance use disorder: prevalence, risk factors and functional disability

Little is known about Autism Spectrum Disorder (ASD) in adults, especially not about ASD with co-morbid Substance Use Disorder (SUD). We wanted to examine how adults with ASD compare to adults with ADHD on prevalence and risk factors for co-morbid SUD, and on disability levels associated with SUD.

We stratified 123 treatment seeking adults with ASD (n=70) or ADHD (n=53), into current, former and no history of SUD (SUD+, SUD(wedge), and SUD-), and conducted interviews to explore associated risk factors and current levels of disability.

Prevalence of co-morbid SUD was higher in ADHD than in ASD in our sample (58% versus 30%, p=0.001). There was no statistically significant difference between ASD and ADHD in risk factors or disability scores. Patients with lifetime SUD started regular smoking earlier in life (OR=5.69, C(95%) 2.3-13.8), reported more adverse family events (OR=2.68; CI(95%) 1.2-6.1), and had more parental SUD (OR=5.36; CI(95%) 1.0-14.5). Disability scores were significantly lower in SUD- and SUD(wedge) groups compared to the SUD+ group.

These findings suggest that ASD and ADHD share similar risk factors for SUD. High disability in ASD and ADHD with SUD may normalize after prolonged abstinence. Early onset of SUD was not associated with more severe disability scores than later onset. Results suggest that a subgroup of patients with former SUD may have a higher level of functioning before the onset of SUD in comparison to those without lifetime SUD.