Ethan Knight is a DPhil candidate in Primary Health Care (with a focus on Addiction) at the University of Oxford and a member of the Oxford Tobacco Addiction Group (OxTAG). His research sits at the intersection of addiction science, behavioural medicine and mental health, with a particular focus on smoking and vaping cessation, relapse, and inequalities in addiction and treatment.

His doctoral research examines how mood shapes early relapse following attempts to quit smoking or vaping, including whether these processes differ among people with a history of mood disorder. His DPhil combines evidence synthesis, secondary data analysis, patient and public involvement (PPI), and an NHS-based prospective study to investigate the relationship between acute post-quit mood and subsequent relapse.

Before beginning his DPhil, Ethan worked as a Research Assistant at Oxford across tobacco addiction and health behaviours research. Within OxTAG, he contributed to the TRIDENT programme investigating smoking reduction among people with severe mental illness, led evidence syntheses on factors influencing switching from cigarettes to e-cigarettes, and led PPI activities. He also conducted quantitative research on alcohol labelling and purchasing behaviour. Ethan holds an MRes in Neuroscience and a BSc in Psychology from Newcastle University, where his research examined the neurobiology of addiction, including the effects of acute alcohol consumption on brain activity and risk-taking, alongside social influences on alcohol consumption.

Across his work, Ethan is particularly interested in the behavioural and psychological mechanisms underlying addiction and relapse, their interaction with mental health, and how this evidence can inform more effective and equitable approaches to smoking and vaping cessation.

Abstract

Acute post-quit mood and early relapse to smoking or vaping: A systematic review

Aims: Early relapse after smoking or vaping cessation is common, and the first four weeks strongly predict longer-term abstinence. Acute post-quit mood disturbance may be a modifiable relapse mechanism, but evidence has not been systematically synthesised during this critical period. We aimed to review and meta-analyse associations between mood within four weeks post-quit and relapse within 12 weeks, including variation by intervention type and psychiatric history.

Methods: We searched MEDLINE, Embase, PsycINFO, CENTRAL, CINAHL, and Web of Science in March 2026 for prospective adult smoking/vaping cessation studies. Eligible studies assessed mood within four weeks post-quit and reported relapse or abstinence within 12 weeks. Screening is complete; extraction follows a partially duplicate process. Risk of bias will be assessed with the Newcastle–Ottawa Scale. Random-effects meta-analyses will pool absolute post-quit mood and mood-change estimates.

Results: We identified 18,149 records and removed 8,971 duplicates. Of 9,178 records screened, 20 studies currently contribute eligible data, and authors of a further 20 studies have been contacted for additional estimates. Evidence to date implicates post-quit anhedonia, depressive symptoms, anxiety sensitivity, and related affective processes in early relapse. Final meta-analytic and narrative synthesis results will be presented.

Conclusions: Early post-quit mood disturbance appears to be a clinically relevant, time-sensitive relapse mechanism after smoking and vaping cessation. By quantifying associations during the first four weeks and linking them to relapse within 12 weeks, this review will clarify when mood matters most and inform the development and optimisation of interventions targeting affect during the period of greatest relapse vulnerability.