Development of an intervention to improve contraceptive use amongst adolescents
The main aim of this thesis was to identify key psychological variables associated with effective contraceptive use to target within an intervention aimed at improving contraceptive use amongst adolescents, since rates of pregnancy amongst UK adolescents remain the highest in Western Europe (Summerfield & Babb, 2004). A further aim was to implement and evaluate such an intervention. A qualitative interview study was conducted with 18 adolescents in order to inform the development of measures for a longitudinal questionnaire study. The questionnaire study was conducted with 291 adolescents to assess which of 17 predictor variables were best at discriminating between less effective and more effective contraceptive users. Analysis identified three variables, from the original 17 predictors, to target within an intervention, namely self-efficacy, control beliefs and anticipated regret. Materials for four intervention conditions were developed. One condition focused on manipulating the similar constructs of self-efficacy and control beliefs, a second focused on anticipated regret, a third combined the materials from the first two conditions, and a fourth acted as an information-only control. Baseline measures of control beliefs, self-efficacy and anticipated regret were taken from 414 adolescents, alongside measures of stages of change (SOC from the transtheoretical model; TTM; Prochaska & DiClemente, 1983), the other constructs from the theory of planned behaviour (TPB, Ajzen, 1988), and a self-report measure of behaviour. One week later, the intervention was implemented and immediate post-intervention measures of the psychological variables taken. Four to five weeks post intervention follow-up measures of the psychological constructs, SOC and behaviour were taken. Analysis of the data showed that levels of five psychological constructs, including self-efficacy, anticipated regret and intention to use contraception had significantly increased over the course of the intervention. Self-reported contraceptive behaviour also showed significant increases amongst a sub-sample of sexually active participants who had relatively low intentions to use contraception at the outset of the intervention. This increases occurred however, regardless of the condition of the intervention. These findings represent an extremely positive outcome for behavioural change research and have important wider implications. Since it seems likely that the questionnaires rather than intervention materials were responsible for observed changes, the findings demonstrate the difficulty in differentiating between the impact of actual intervention material and the questionnaires used to measure their effectiveness. There is also evidence that it may be advantageous to tailor future interventions to specific sub-groups of populations. Suggestions for future research are provided and the implications of the findings for pregnancy prevention within the UK are also addressed.