Can the Theory of Planned Behaviour mediate the effects of age, gender and multidimensional health locus of control?

Objectives. The present paper reports two studies designed to test the ability of the theory of planned behaviour (TPB) to mediate the effects of age, gender and multidimensional health locus of control (MHLC) on behavioural intentions and behaviour. Design. Two studies are reported. Study 1 (N = 124) employed a cross-sectional design and examined three self-reported health-related behaviours: safe sex (condom use), binge drinking and drink-driving. Study 2 (N = 20 1) employed a prospective design and examined actual attendance at health screening. Methods. Respondents completed questionnaires containing measures of MHLC and TPB. The data were analysed using a combination of bivariate correlations and hierarchical multiple regression. Results. Study 1 showed that the TPB was a superior predictor of health-related behavioural intentions than both demographic variables and MHLC. Study 2 corroborated the findings of Study 1, and showed that TPB variables were useful predictors of actual behaviour, although the TPB failed to fully mediate the effects of gender on screening attendance. Conclusions. Whilst the TPB accounted for significant proportions of the variance in health-related behavioural intentions and behaviour, it failed to completely mediate the effects of demographic variables. Future work is required to identify social cognitive variables that will fully mediate the effects of demographics.