Personality, Motives, and Substance Use among Opioid Agonist Therapy Clients

Abstract

Background: The Four Factor Personality Vulnerability model (Castellanos-Ryan & Conrod, 2012; Conrod, Pihl, et al., 2000) implicates four personality traits in conferring vulnerability to substance misuse: sensation seeking (SS), impulsivity (IMP), anxiety sensitivity (AS), and hopelessness (HOP). Although the role of these personality traits has been well studied in the development of substance use behaviors, less is known about the impact of this model among a population at a later stage of addiction. My dissertation sought to understand how these four traits are involved in the maintenance of addictive behaviour among methadone maintenance therapy (MMT) clients. Method: Across four separate analyses, using both quantitative and qualitative methodologies, I investigated the role of personality in a sample of 138 MMT clients recruited across four different MMT clinics in two Canadian provinces. Study 1 validated the Substance Use Risk Profile Scale (SURPS; Woicik et al., 2009) in this population using Bayesian Confirmatory Factor Analysis. Study 2A developed and tested a novel substance use motives measure to investigate the motivational dynamics of polysubstance use. Study 2B extended these results to also examine interactions between personality and drug class. Study 3 recruited 20 MMT clients scoring high on one of the four personality traits who underwent a semi-structured interview. Interviews were transcribed; thematic analysis was used to code for relevant themes and content analysis was used to examine relative endorsement of thematic codes across each personality type. Results: The SURPS is an appropriate clinical instrument among MMT clients (Study 1). Further, personality is associated with specific forms of recent substance misuse (Study 1) and motives for use (Study 2B). Motives for use vary significantly by drug class, with different motives showing varying levels of state/trait properties (Study 2A). Finally, the relative endorsement of various themes across each personality type suggests a unique cognitive-behavioral profile specific to each trait (Study 3). Conclusions: Taken together, my research suggest that personality is important in explaining the maintenance of substance use behaviours among MMT clients. My dissertation therefore supports the development of personality-matched interventions as a supplement to MMT and a novel tool for fighting the opioid epidemic.