What if I fail? Unsuccessful smoking cessation attempts and symptoms of depression and anxiety: A systematic review and meta-analysis.

Objectives: Evidence that smoking cessation benefits physical and mental health has led to recommendations to support quitting. Unsuccessful quit attempts are common and associated with guilt and frustration; however, their impact on mental health is unclear. This review investigated the association between the success/failure of smoking cessation attempts and changes in symptoms of depression and anxiety.

Design: Systematic review and meta-analysis, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines.

Data sources: Inclusion and exclusion lists of two previous reviews, plus update searches of Embase, Medline and PsycINFO (January 2020–January 2025).

Eligibility criteria: Trials and longitudinal observational studies measuring symptoms of anxiety or depression before and after a smoking cessation attempt, beyond the withdrawal period (6 weeks), in adults who successfully quit and made an unsuccessful attempt.

Data extraction and synthesis: Standardised methods were used for screening and data extraction. Two independent reviewers screened a minimum of 25% and extracted data for 100% of studies. Meta-analyses were conducted using random effects models, and narrative synthesis was used when necessary. Study quality, heterogeneity and publication bias were assessed using the adapted Newcastle-Ottawa Scale, I2 and funnel plots, respectively.

Results: 62 studies were included, representing 36 150 participants. Most featured behavioural smoking cessation interventions and defined successful cessation attempts by self-reported or biologically verified abstinence. Follow-up ranged from 6 weeks to 4 years. Overall, successfully quitting smoking was associated with reduced symptoms of depression (standardised mean difference (SMD)=–0.21, 95% CI –0.27 to –0.16) and anxiety (SMD=–0.22, 95% CI –0.33 to –0.12) compared with unsuccessful quit attempts. Heterogeneity was substantial (I2=50-69%).

Conclusions: Most studies indicated a positive trend in alleviating symptoms of anxiety and depression during a quit attempt. Successful quitters experienced more substantial reductions in these symptoms compared with those who were unsuccessful. Importantly, those who made an unsuccessful quit attempt did not experience worse mental health.