Sleep quality and quantity among University students is a topic of growing concern (Manzar et al., 2015). Emerging adulthood is a vulnerable developmental period characterized by a high frequency of impaired sleep. Previous international studies have shown that poor sleep quality is predominant and concerns 55% of students (Jahrami et al., 2020). Notably, 19% of students complain of insomnia (Jiang et al., 2015). Increased autonomy, academic and social pressure, and irregular sleep-wake times at an age when the circadian rhythm is delayed (Wolfson, 2010) and the central nervous system is still maturing (Drake et al., 2004) could explain the altered sleep patterns in this population. These sleep alterations are all the more concerning because of their detrimental effects on mental and physical health and cognitive capacities, which is especially important for the daily-functioning and academic success of students (Buysse, 2014; Garbarino et al., 2016; Shochat et al., 2014). The Covid-19 health crisis has further aggravated sleep complaints in the French population (Santé Publique France [Public Health France], 2021).

Cannabis use, despite being illegal in France, is common among young adults within the country: in 2020, 13.9% used it monthly and 4.0% daily (Nézet et al., 2021). While controversies about its legalization or decriminalization have been ongoing for decades, its high level of consumption in young French adults is of concern as cannabis abuse could set the stage for poor mental and physical health outcomes that persist through adulthood (Brown et al., 2001).

In particular, some studies have explored the effect of cannabis use on sleep as an important determinant of health (Angarita et al., 2016; Babson et al., 2017; Kesner and Lovinger, 2020). Early contributions focused on experimental assessment of the immediate effects of cannabis on sleep in small samples via polysomnography (Barratt et al., 1974; Freemon, 1972; Karacan et al., 1976; Nicholson et al., 2004). These studies showed that acute cannabis use decreases sleep latency and wake after sleep onset, increases slow wave sleep, and decreases rapid-eye movement sleep, whereas withdrawal has the opposite effect (Angarita et al., 2016; Babson et al., 2017; Kesner and Lovinger, 2020). However, chronic cannabis users may develop a tolerance for acute effects, leading to increased sleep latency and decreased slow wave sleep (Babson et al., 2017), which is essential to cerebral restoration, recovery, and memorization (Roth, 2009). More recently, observational studies have investigated the relationship between sleep and cannabis use in real-life conditions (Johnson and Breslau, 2001; Kwon et al., 2021; Leger et al., 2022; Navarro-Martínez et al., 2020; Ogeil et al., 2015; Pasch et al., 2012; Roane and Taylor, 2008; Troxel et al., 2021). Some of these studies found an increased frequency of sleep disturbances with increased cannabis use in adolescents (Kwon et al., 2021; Pasch et al., 2012) and young adults (Roane and Taylor, 2008; Troxel et al., 2021).

Few studies have focused on University students, although they are particularly affected by sleep complaints. Sample sizes of these studies were often limited and they did not take into account important suspected confounders in the association such as mental health disorders, economic situation, or sleeping drug intake (Hunt and Eisenberg, 2010; Navarro-Martínez et al., 2020; Phillips et al., 2018; Wang and Bíró, 2021; Yurasek et al., 2020). Besides, sleep measurement was usually focused on one single dimension (i.e., insomnia or sleep quality) and cannabis use on one frequency (used/not used in the past month) (Pasch et al., 2012; Troxel et al., 2021).

The main aim of this study was to have a thorough analysis of the association between cannabis use and sleep complaints and in a large sample of University students, and to take into account several important individual and behavioral characteristics. Our secondary aim was to evaluate the role of previous mental health diagnoses in this association.