Serial mediation between self-efficacy and motivation as a mechanism of change in tobacco cessation: analysis of the Guided Self-Change therapy effectiveness

Background: Behavioral interventions are effective for smoking cessation; however, little is known about the underlying mechanisms of treatment outcomes. Self-efficacy and motivation to quit are two central mediators of therapy success, however, their interaction during tobacco cessation remains unclear. The aims of this study were to analyze the effectiveness of Guided Self-Change (GSC) therapy for smoking cessation and to examine parallel and serial mediation between self-efficacy and motivation during therapy.Method: We conducted a one-group pretest-posttest design with the participation of 145 treatment-seeking smokers (age = 55.8 +/- 10.3 years; 59.3% women) from the General University Hospital of Alicante. We assessed participants' daily tobacco use, self-efficacy, and motivation to quit at baseline and at the end of treatment. Descriptive, bivariate, and mediation analyses were performed.Results: A total of 49% (n = 71) of participants completed GSC therapy (3-5 sessions), of which 52.1% (n = 37) stopped using tobacco after treatment (McNemar's p < 0.001; theta = 5.85). Mediation analyses showed GSC therapy significantly increased (p < 0.01) both self-efficacy (a(1)=1.19; 95%CI = 0.47, 1.91) and motivation (a(2)=1.95; 95%CI = 1.34, 2.56). However, only the serial path from self-efficacy to motivation to quit showed significant indirect effects in tobacco reduction (a(1)a(3)b(2)=-0.29; 95%CI=-1.1, 0.03; Z=-4.36; p < 0.001).Conclusions: GSC therapy demonstrated effectiveness in quitting smoking by partially increasing self-efficacy, which in turn enhanced motivation to quit leading to a reduction of use. These findings expand empirical knowledge about theorized mechanisms of change in addictive behaviors that could contribute to improving psychological interventions.