The purpose of this study was to test the extent that constructs from two theoretical models (self-regulatory theory and social cognitive theory) mediated change in outcomes following a self-management intervention. One hundred and twenty four individuals with type 2 diabetes who had participated in a randomised controlled trial of a diabetes self-management programme were analysed for the extent that illness beliefs and self-efficacy mediated change in self-management behaviours and illness specific quality of life. Exercise specific self-efficacy significantly mediated change in exercise at three months (B = .03; .01, p < .05) while monitoring specific self-efficacy mediated change in monitoring behaviour at both three (B = .04; .01, p < .01) and nine months follow-up (B = 5.97; 1.01, p < .01). Belief in control over diabetes mediated change in illness specific quality of life at three months (B = -.07; .28, p < .05) and nine months (B = .79; .28, p < .01) follow-ups, as well as change in exercise behaviour at immediately post-intervention (B = -.12; .17, p < .05). Behaviour-specific self-efficacy may have a stronger role in mediating self-management behaviours than illness beliefs; however, belief in control over diabetes may be important to manipulate for change in quality of life. This suggests different theoretical constructs may mediate change dependent on outcome.
Keywords: illness beliefs; mediation; self-efficacy; self-management.