Degree Name

Doctor of Philosophy (Clinical Psychology)


School of Psychology


With persistent and chronic use of alcohol and drugs, structural and functional changes occur in the brain, contributing to the development and maintenance of substance use disorder (SUD). The cyclic nature of addiction is increasingly understood in a neuroscientific framework. Influential theories describe allostatic changes that occur over time as the initial highly rewarding effects of substances subsequently lead to reduced capacity of prefrontal brain regions to exert effective self-regulation, while an increasingly reactive amygdala-striatum system becomes progressively more vulnerable to substance-cues, stress, negative affect, and compulsive substance use (Koob & Volkow, 2016; Noël, Brevers, & Bechara, 2013; Volkow & Morales, 2015). The resulting cognitive deficits are one of the most commonly reported risk factors for dropout from addiction treatment (Brorson, Ajo Arnevik, Rand-Hendriksen, & Duckert, 2013). Recently it has been proposed that interventions designed to improve cognition may bolster SUD treatment outcomes and increase the likelihood of long-term recovery from addiction (Verdejo-García, 2016). This thesis aimed to investigate the potential for neuropsychological screening and cognitive training interventions to improve SUD treatment outcomes. The first study of this thesis (Chapter 2) assessed cognitive functioning in an SUD sample in residential treatment (N = 128), with findings indicating that almost half (43.8%) were identified as cognitively impaired, compared to 16.2% of controls (N = 37). History of head injury was a significant determinant of cognitive impairment and cognitive impairment was associated with higher levels of psychological distress. Study two evaluated a cognitive remediation intervention developed to specifically target executive dysfunction and delivered within residential SUD treatment – in an all-female sample inclusive of those with comorbidities including psychiatric diagnoses and history of head injury (Chapter 3). A threemonth follow-up was included to assess outcomes over time (Chapter 4). Lastly, the relationships between executive functions (EFs) and emotion regulation were investigated iv (Chapter 5), given the proposed links between EFs and self-regulation capacity (Hofmann, Schmeichel, & Baddeley, 2012), and the significant role of emotion dysregulation in the aetiology and maintenance of SUDs (Wilcox, Pommy, & Adinoff, 2016). Findings regarding the evaluation of the intervention indicated that the cognitive remediation group (CR; N = 16) improved in an inhibition task, inventory-based assessment of EFs, self-reported impulsivity and self-control, and quality of life, relative to controls, who participated in treatment as usual (TAU; N = 17). Three-month follow-up outcomes of the intervention indicated no significant differences between the CR (N = 12) and TAU (N = 12) groups with regard to quality of life and self-reported self-control, cravings, and likelihood of relapse. The CR group demonstrated sustained improvements in inventory-based assessment of EFs and a higher rate of treatment completion (37.5%) compared to the TAU group (5.9%), however, treatment completion may have been confounded by the unexpectedly longer duration of treatment at baseline observed in the CR vs. TAU group. Investigation of relationships between EFs and emotion regulation at baseline in the entire sample (N = 50) indicated that task-switching, inventory-based assessment of EFs, and personality disorder indicators uniquely predicted emotion regulation difficulties. Mediation analysis found a significant indirect effect of task-switching performance on emotion regulation difficulties, through personality disorder indicators. Taken together, these findings provide preliminary evidence for the use of cognitive remediation to improve cognition in a residential SUD sample, including those with the often-excluded comorbidities of psychiatric diagnoses and history of head injury. These findings have utility in informing the continued development and evaluation of novel cognitive remediation interventions for SUD populations.