Latent Impulsivity Subtypes in Substance Use Disorders and Interactions with Internalizing and Externalizing Co-Occurring Disorders

Abstract

This study explored the clinical importance of latent impulsivity subtypes within a sample of individuals with substance use disorders (SUDs) and high rates of co-occurring disorders (CODs) receiving residential treatment, aiming to assess the heterogeneity of the associations between SUDs and CODs across such impulsivity subtypes. The abbreviated Barratt impulsiveness scale was used to assess motor and cognitive (attentional and nonplanning) impulsivity, a structured interview for diagnosis of SUD and CODs, and other clinimetric measures for severity of substance use. Latent class analysis was conducted to extract subgroups of impulsivity subtypes and Poisson regression to analyze effects of interactions of classes by CODs on severity of substance use. 568 participants were evaluated. Results featured a four-class model as the best-fitted solution: overall high impulsivity (OHI); overall low impulsivity; high cognitive-low motor impulsivity; and moderate cognitive-low motor impulsivity (MC-LMI). OHI and MC-LMI concentrated on most of the individuals with CODs, and individuals within OHI and MC-LMI showed more severity of substance use. The expression of this severity relative to the impulsivity subtypes was modified by their interaction with internalizing and externalizing CODs in very heterogeneous ways. Our findings suggest that knowing either the presence of trait-based subtypes or CODs in individuals with SUDs is not enough to characterize clinical outcomes, and that the analysis of interactions between psychiatric categories and behavioral traits is necessary to better understand the expressions of psychiatric disorders.

Keywords: co-occurring disorders; externalizing disorders; impulsivity; internalizing disorders; latent class analysis; substance use disorders.

Figure 1

Graphical representation of the analytical model. In the first step, the categorical latent variable (Impulsivity subtypes) was estimated using LPA. In the second step, interactive terms (Internalizing disorders × impulsivity subtype and externalizing disorders × impulsivity subtype) were included and tested using Poisson regression, to determine the differential effect across impulsivity subtypes.

Figure 2

Latent classes of impulsivity in polysubstance users in residential treatment. Notes: n = 568. Values are presented after correction for inverted response options (e. g., “I concentrate easily”), so they indicate unidirectional level of impulsivity. C, class; OHI, overall high impulsivity; HC-LMI, high cognitive-low motor impulsivity; MC-LMI, moderate cognitive-low motor impulsivity; OLI, overall low impulsivity.