Psychological and behavioural within-participant predictors of adherence to oral HIV Pre-Exposure Prophylaxis (PrEP)

Alison Taylor

Research output: ThesisDoctoral Thesis

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Systematic Review
The literature highlights that adherence is critical for maximizing the effectiveness and public health impact of PrEP to prevent HIV infection. Understanding the factors associated with PrEP adherence/non-adherence is crucial to guiding the development of a theoretical framework as well as PrEP adherence interventions. Studies investigating medication adherence within different study populations (i.e HIV positive individuals), examining predictors of PrEP uptake or exploring hypothetical facilitators and barriers to PrEP use, have limited generalisability to understanding adherence amongst actual PrEP users. Therefore, the current systematic review synthesised the literature exploring factors related to PrEP adherence amongst MSM. Studies were included if they reported statistical relationships with, or given reasons for, PrEP adherence/non-adherence amongst MSM PrEP users at high-risk of HIV acquisition. Twenty studies (qualitative n=5, quantitative n=15) met the review’s inclusion criteria. The review described and evaluated the reviewed studies, synthesised the data, and the direction of relationships were examined. Across studies, twenty factors were measured and analysed in relation to PrEP adherence. Eleven factors showed inconsistent findings across studies and three factors were only measured once. Variables examined by three or more studies where the majority reported or showed a relationship with PrEP adherence included: older age, stable housing, higher levels of HIV risk perception and actual risk behaviours, routine and planning, lifestyle factors (i.e. less travel and being less busy), less anticipated stigma if PrEP use was disclosed, not being African-American, less anticipated or actual side-effects and support from others. The review demonstrated that adherence to PrEP may be influenced by several factors at individual, interpersonal and structural levels. The review highlighted potentially modifiable factors related to PrEP adherence which could be targeted in PrEP adherence interventions. It also highlighted factors which may vary within-individual dependent on the situation. Future research could examine modifiable situational variables (psychological and behavioural) to gain a clearer understanding of how these factors could impact adherence.

Empirical Project
The effectiveness of PrEP is variable, explained by differences in PrEP adherence. PrEP adherence is often inconsistent within individuals, whereas most studies only investigate adherence between individuals. Understanding psychological and behavioural correlates of PrEP adherence is important to develop effective adherence interventions. This study investigated within-participant behavioural and psychological differences between adherent and non-adherent PrEP episodes in men who have sex with men (MSM), informed by theory (the Information-Motivation-Behavioural Skills model). Sixty-seven HIV-negative MSM at high-risk of HIV acquisition were recruited from two London sexual health clinics. All participants had followed a daily dosing PrEP regimen for at least three months and had shown inconsistent adherence (i.e. had one day when a dose was taken and one day when a dose wasn’t taken) in the previous month. Participants completed a questionnaire measuring psychological and behavioural variables for both an adherent and non-adherent episode. Paired t-tests, McNemar’s chi-square tests and a conditional logistic regression (CLR) model were used to analyse associations between situational behavioural and psychological factors and adherent and non-adherent events. Lower reported information about PrEP, lower behavioural skills related to PrEP use and lower positive affect were associated with non-adherent episodes. There were no significant differences in negative affect or PrEP motivation between episodes. A CLR model including information, behavioural skills and positive affect was significantly predictive of non-adherent episodes, although only behavioural skills was statistically significant independently. Behavioural factors including weekend days, lack of reminders, non-normality of the day, being out of the home, not being alone and substance use were also associated with PrEP non-adherence. Findings suggested that situational psychological factors are important for PrEP adherence. Theoretically, findings give support to some aspects of the IMB model to help explain PrEP adherence, however, also highlight predictors related to PrEP adherence which are not acknowledged within the model (i.e. situational behavioural factors such as location or positive affect). Adherence interventions should consider focusing on potentially modifiable situational variables (psychological and behavioural).
Original languageEnglish
Awarding Institution
  • Department of Psychology
  • Evangeli, Michael, Supervisor
  • Gafos, Mitzy, Supervisor, External person
Award date1 Nov 2018
Publication statusUnpublished - 2018

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