BACKGROUND AND AIM: There is evidence that smoking cessation may improve depression and anxiety symptoms. We assessed the feasibility of implementing and trialling a smoking cessation intervention in services providing cognitive behavioural therapy (CBT) for common mental illness. DESIGN, SETTING AND PARTICIPANTS: This study was a pragmatic, two-armed, randomised, multi-centre, acceptability and feasibility trial of a co-designed smoking cessation intervention (ISRCTN99531779) involving United Kingdom National Health Service (NHS)-funded services treating depression or anxiety among four NHS Trusts. Participants comprised adult daily smokers starting CBT for depression or anxiety [mean age 35.6 years, standard deviation (SD) = 12.7, 89.6% white] who smoked 14.3 (SD = 8.2) cigarettes/day with mean Generalised Anxiety Disorder Questionnaire-7 (GAD-7) and Patient Health Questionnaire-9 (PHQ-9) scores of 13.1 (SD = 4.9) and 14.5 (SD = 6.0). Sixty-eight participants were allocated to the treatment group and 67 to control. INTERVENTION AND CONTROL: Both groups received CBT for depression or anxiety. The treatment group also received up to 12 sessions of integrated smoking cessation support. The control group was signposted to smoking cessation services post-treatment. MEASUREMENTS: Follow-up was at 3 and 6 months. The primary outcome was 'study completion' by 3 months. Other outcomes included acceptability, satisfaction, feasibility, data completeness and mental health. FINDINGS: At 3 months, treatment did not affect study completion [odds ratio (OR) = 0.81, 95% confidence interval (CI) = 0.31 to 2.09], did not harm mental health (PHQ-9 difference: coefficient 0.01, 95% CI = -2.19 to 2.22)
GAD-7: coefficient 0.65, 95% CI = -1.59 to 2.90), but increased abstinence rates (OR = 8.69, 95% CI = 1.11 to 396.26). Recruitment was acceptable and key stakeholders were satisfied with the intervention. CONCLUSIONS: Among UK adult smokers receiving CBT treatment for depression or anxiety, a smoking cessation intervention within the CBT treatment was well received, did not interfere with the primary treatment goals and increased smoking cessation.