Background:
Humans’ natural inclination to be more or less active at a certain time during the day is known as chronotype. Three main phenotypic variants of chronotype exist: morning, evening, and neither. These features are known to be connected with stimulant consumption (e.g. alcohol, caffeine, and tobacco) and nowadays research is focusing on the relationship between chronotypes and tobacco smoking or vaping.

Objective:
The aim of this systematic review was to evaluate the scientific evidence on the associations between human chronotype and tobacco smoking or vaping.

Methods:
On 29 April 2022 a systematic search of the scientific literature was performed on three different databases (PUBMED, Web of Sciences, Scopus). Studies assessing chronotype and its relationship with tobacco smoking or vaping were included. Any type of study design, in English, sampling any age group from all over the world was considered. Quality assessment was performed with Joanna Briggs Institute Critical Appraisal tools.

Results:
The search yielded 538 articles, of which six (one retrospective case-control and five cross-sectional studies) were included in the review. Despite differences in quality, participants’ characteristics and the lack of studies on vaping, most of them reported a relationship between tobacco smoking and chronotypes. In particular, smokers tend to be more of an evening type, have larger coffee and alcohol consumption and greater differences in waking up time between weekdays and weekends (Wittmann et al. 2010, p=0.001).

Conclusions:
This review aims to systematically characterize the smoking effects on a specific chronotype. Albeit that this topic has potential, a small number of studies were published. This review underlines the importance for future studies to focus on this field, mostly considering the fact that adjusting smoking cessation treatment based on an individual’s chronotype attitude, could increase smoking cessation and psychological well-being.