Impaired Olfactory Function In Substance Use Disorder

The sense of smell plays a key role in guiding motivated behavior, and olfactory function is impaired in clinical populations with dysfunctional approach-avoidance behavior, including major depressive and alcohol use disorder (AUD). However, whether olfactory impairments are also observed in individuals with substance use disorders (SUDs) other than AUD is currently unknown. This study aimed to evaluate the relationship between olfactory function and SUDs. We tested olfaction in 40 individuals with substance use disorders (SUDs) other than AUD using the Sniffin Sticks odor identification and olfactory threshold tests, versus 112 controls. Group differences were assessed with linear regression models, with diagnosis (SUD vs. controls) as a predictor, controlling for age, sex and smoking. Across a diverse range of substances used, individuals with SUDs had significantly lower identification scores than those in the control group. In contrast, olfactory thresholds did not differ significantly by diagnosis overall. However, exploratory analyses showed that men with SUDs had lower olfactory threshold scores (i.e., higher thresholds) than men in the control group, a difference that was absent in women. These results suggest that olfactory function is impaired in individuals with SUDs relative to controls. There are several plausible pathways by which differences in olfaction could be related to differences in hedonic processing, but longitudinal studies are needed to clarify the timing of olfactory impairment relative to substance use or SUD symptomatology.