Association Between Family Factors and Illicit Polysubstance Use Amongst Methadone Maintenance Patients with Opioid Use Disorder

Opioid use disorder (OUD) is increasingly prevalent in North America. Methadone Maintenance Therapy (MMT) is an opioid substitution therapy used to relieve symptoms of withdrawal, and to manage OUD symptoms. Despite MMT’s overall effectiveness, individual treatment outcomes vary, and little research explores why these differences exist. Considering the association between genetic vulnerability, including family factors, and substance use disorders (SUDs), this study investigated the relationship between family factors and treatment outcomes in individuals with OUD receiving MMT. Patients and Methods: This cross-sectional study included a sample of 973 adult patients with OUD in MMT. Family factors were defined as number of relatives with an SUD, and their degree of genetic relatedness to the proband. Patient-related outcomes were determined by measuring illicit opioid and non-opioid use during MMT. A significant association was found between number of family members with an SUD and the proband’s illicit opioid use (OR = 1.08, 95% CI = 1.01, 1.16; P = 0.03). No significant association was found between genetic relatedness and the proband’s illicit opioid and non-opioid use, nor between number of family members with an SUD and the proband’s non-opioid use. These results suggest a role of shared familial environmental factors in OUD treatment outcomes. Specifically, OUD patients with a family history of substance use are at higher risk of relapse during MMT. Based on these findings, healthcare providers should consider stratifying their OUD patients based on family history of SUDs, and providing additional support to those with a positive history to improve their MMT outcomes.