Clinical and psychosocial predictors of attendance and drug use in heroin users undergoing treatment

The main aim of this thesis is to evaluate the Theory of Planned Behaviour's ability to identify predictors of intention and behaviour. The population of interest are heroin users; the behaviours are attendance at treatment services and heroin use during drug treatment. The thesis is divided into four broad sections. First, a literature review considers the impact of heroin use on the individual and society; the relevance of drug treatment to enable reductions of drug related harms and the predictors associated with poor treatment outcomes. It goes on to provide justification for the use of the TPB over other models of behaviour change and discusses the limitations associated with its application. The TPB is shown to be a useful predictor of behaviour and intentions in general, although there is no research considering the prediction of attendance for drug treatment and future heroin use. Secondly, a qualitative study explores whether the TPB is an appropriate framework for predicting behaviour in this population by undertaking interviews designed to investigate whether drug users can think about stopping drug use in relation to TPB constructs. A review of previous qualitative research and findings from this study suggest that the TPB would be an appropriate framework for use in this domain.