Additive effectiveness of contingency management on cognitive behavioural treatment for smokers with depression: Six-month abstinence and depression outcomes.

Abstract

Depression and smoking co-occur at high rates and there is a lack of evidence on the efficacy of treatments specifically tailored to this population. This randomized controlled trial sought to compare the effectiveness of cognitive behavioural treatment (CBT) combined with behavioural activation (BA) and the same treatment protocol plus contingency management (CM). A sample of 120 adult smokers (70.8%: females) with severe depressive symptoms were randomly allocated to: CBT + BA (n = 60) or CBT + BA + CM (n = 60). Smoking and depression outcomes were reported at end of treatment, 1-, 2-, 3-, and 6-month follow-ups. Self-reported smoking status was biochemically verified, and depression was assessed using the Beck Depression Inventory-II. At end of treatment, the overall quit rate was 69.2% (83/120). CM showed an additive effect on CBT + BA in enhancing abstinence rates. The significant effect of group [F(1,155) = 9.55, p =  .0024], time [F(4,96) = 7.93, p < .0001], and group by time interaction [F(4,96) = 6.12, p =  .0002], indicated that CM is more effective for generating longer durations of abstinence beyond those of CBT+BA. All treatment conditions equally promoted sustained reductions in depression across time [F(1,111) = 0.53, p =  .4665]. A greater number of days of continuous abstinence and lower depressive symptoms mutually influenced each other. Depressed smokers achieve high cessation rates without suffering negative mood changes. Quitting smoking is not detrimental and adding CM to CBT + BA enhances long-lasting abstinence rates while promoting large depression improvements.