Integrating Health Psychology into Hepatitis C treatment
: a self-efficAcy intervention to reDuce injecting risk behAviour and hePatitis c reinfecTion rates (ADAPT)

Student thesis: Doctoral ThesisDoctor of Philosophy


This thesis is divided into two main sections. The introductory section comprises studies one and two, while the pilot RCT section comprises studies three and four. The initial two studies were carried out to inform the latter two.

Injecting behaviour in people who inject drugs (PWID) is a significant risk factor for hepatitis C virus (HCV) infection. Self-efficacy has been shown to be associated with injecting risk behaviour. The risk of HCV re-infection in people who inject drugs (PWID) treated for HCV remains high when sharing of injecting equipment continues post-treatment.

The first study aimed to assess the effectiveness of forming implementation intentions to reduce substance use. Implementation intentions are self-regulatory processes which help achieve health-related behaviour change. A systematic search of published literature was conducted to gather evidence on the effectiveness of the use of implementation intentions for substance use behaviours from existing studies. The findings of studies selected from this search were collated to carry out a meta-analysis in order to produce evidence for the effectiveness of implementation intentions within substance use behaviours, informing study 3. Significant effects were found of implementation intentions on alcohol use and tobacco smoking. A small non-statistically significant result was reported for self-efficacy. No studies were found in the systematic search on the use of implementation intentions for the reduction of illicit drug use.

The second study aimed to investigate possible injecting behaviour changes associated with clinical treatment of HCV. The chapter reports the results from a data analysis exercise completed in January 2018 on participants of Eradicate-C, a clinical trial of HCV treatment in PWID. A significant reduction in weekly injecting frequency was reported by participants on treatment (n=84).

The third study, ADAPT, represents the main study of this thesis. ADAPT is a pilot randomised controlled trial testing the use of implementation intentions with people who inject drugs on treatment for hepatitis C to increase self-efficacy and reduce sharing of injecting equipment. It involved four visits over the course of participants’ HCV treatment. The intervention was carried out during the second visit. Psychosocial factors measured during visit 1 of ADAPT (n=50) were explored as predictors of the primary outcome, injecting risk behaviour. A regression analysis was performed with bootstrapping to test a predicting model of injecting risk behaviour as explained by injecting frequency, identification with family and identification with drug network. Identification with drug network was the only significant predictor of injecting risk behaviour. Correlation analyses showed strong correlations between self-efficacy, injecting risk behaviour, injecting frequency and group identification with drug network. No significant differences were found between control and intervention groups on self-efficacy and injecting risk behaviour (n=32).

The fourth study is a sub-study of ADAPT. This study was a qualitative investigation of the lived experience of PWID who are infected with HCV. Thematic analysis was used to analyse the findings of the study. It was run concurrently with ADAPT. Three overarching themes were identified in the interview transcripts: 1. “Changing illness perception”; 2. “Shifting agency”; 3. “Treatment adherence”.

The last chapter of the thesis aims to integrate the findings of study 3 and 4 into one final discussion. It also aims to provide a narrative reflection on the lessons learnt whilst planning and conducting the research with a hard-to-reach population, concluding with implications of the findings, the limitation of the studies and the suggestions for future research.
Date of Award2021
Original languageEnglish
SupervisorFabio Sani (Supervisor) & John Dillon (Supervisor)

Cite this