Clinically, OUD often co-occurs with other types of substance use disorder and other psychiatric conditions. Several studies have evaluated the possibility of a common genetic component across different types of SUDs (Compton et al., 2007; Vaughn et al., 2018). In a recent study from the GWAS & Sequencing Consortium of Alcohol and Nicotine use (GSCAN), multiple genetic loci appeared to affect phenotypes related to both tobacco and alcohol use, suggesting a strong etiological relationship(Liu et al., 2019). To quantitatively estimate the shared genetic factors across SUDs, we calculated the genetic correlations between OUD and two other major SUDs, namely alcohol and nicotine use disorder. As expected, strong positive correlations were observed, with the strongest relationship between nicotine and opioid use disorders. Previous studies have found that opioid receptor binding is correlated with nicotine’s dependence and rewarding effects(Kuwabara et al., 2014). Our results provide further evidence for the connection between nicotine and opioid misuse and generally support the validity of our methodology.
