Patterns of Polysubstance Use and Simultaneous Co-use in High Risk Young Adults

Background: Polysubstance use (PSU) is associated with worse prognosis and poorer physical and mental health compared to single substance use. The current study provides information about PSU patterns by examining a diverse range of alcohol/substance use behaviors ranging from low-level experimentation to indicators of severe abuse. In addition, the current study, for the first time, examines how simultaneous co-use of multiple substances cluster with other more commonly studied PSU behaviors.

Methods: Latent Class Analysis was used to identify patterns of substance use, in a sample of young-adults (n = 2098), using 25 items from the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA-II) including: items assessing severity of problems with alcohol, cannabis, stimulants, opiates, and sedatives; items assessing # of lifetime uses; items assessing simultaneous co-use of all combinations of substances. Then the association of class membership and age, antisocial and impulsive personality, experience seeking, anxiety, and neuroticism was examined using Multinomial Regression.

Results: Fit indices (i.e. AIC, SSABIC, and entropy) and interpretability of classes supported a five-class solution: "Low Problems" (32% of sample), "Alcohol Primary" (11%), "Alcohol and Cannabis" (25%), "Moderate PSU" (23%), and "Severe PSU" (9%). Simultaneous co-use behaviors discriminated between lower and higher severity groups. Externalizing personality constructs robustly predicted membership in the "Moderate" and "Severe" PSU classes compared to the "Alcohol Primary" class.

Conclusions: PSU patterns followed an additive pattern of use with lower severity classes using alcohol/cannabis and more severe classes using other illicit substances in addition. Co-use items provided valuable information about PSU severity.