Examining the relationship of concurrent obesity and tobacco use disorder on the development of substance use disorders and psychiatric conditions: Findings from the NESARC-III.

Background: Multimorbidity is linked to worse health outcomes than single health conditions. However, recent studies show that obesity may reduce the risk of developing substance use disorders (SUDs), particularly in vulnerable populations. We investigated how comorbid obesity and tobacco use disorder (TUD) relate to the risk of SUDs and psychiatric conditions. Methods: Data was used from 36,309 individuals who completed the National Epidemiological Survey on Alcohol and Related Conditions - Wave III. Individuals who met the DSM-5 criteria for TUD in the last year were defined as the TUD group. Obesity was defined as having a body mass index (BMI) greater than 30 kg/m2. Using this information, individuals were grouped into categories, with people being identified as either having obesity, TUD, both obesity and TUD, or not having either obesity or TUD (comparison). Groups were compared against their comorbid diagnoses of either an additional SUD or psychiatric conditions. Results: Controlling for demographic characteristics, we found that individuals with obesity including those individuals with TUD, had lower rates of comorbid SUD diagnosis than individuals with TUD alone. Additionally, individuals with combined TUD and obesity, and those with TUD alone, had the highest rates of comorbid psychiatric disorder diagnosis. Conclusions: The current study aligns with previous research suggesting that obesity may reduce risk of substance use disorders, even in individuals who have other risk factors promoting harmful substance use (e.g., tobacco use). These findings may inform targeted intervention strategies for this clinically relevant subpopulation.