Objective: Those with comorbid substance use disorders (SUDs) are a particularly vulnerable group. Information regarding the nature of these comorbidities and how they relate to receipt of substance use treatment could reduce the treatment gap that exists among those with comorbid SUDs.
Method: Public-use data from the 2015-2017 National Surveys on Drug Use and Health was used to analyze past-year SUD comorbidity combinations among 12 substances and the relationship between these combinations with past-year treatment in adults (N = 128,740).
Results: In all, 7.9% of adults had at least one SUD in the past year (6.7% had one SUD, 0.9% had two SUDs, and 0.3% had three or more). Conditioning on specific SUDs, the prevalence of having additional SUDs ranged from 14.9% (alcohol) to 85.1% (hallucinogens). The four most common SUD combinations all included alcohol use disorder. Alcohol and marijuana use disorder was the most common comorbidity combination and had the lowest receipt of treatment. Compared to those with one SUD, adjusted odds of receiving treatment were almost two times greater for those with two SUDs, and more than four times greater for those with three or more SUDs. Treatment prevalence was lower for those who had higher family income and education, were not employed full time, were married, were younger than age 26 years or older than age 50 years, and were Asian.
Conclusions: Even though the treatment gap is reduced among those with multiple SUDs, it remains large. The most common and undertreated comorbid SUD combinations, in conjunction with the most underserved groups, could be targeted to facilitate treatment uptake.