Our main results could be summarised as follows: (i) alcohol (80%), tobacco (40.3%) and cannabis (34.0%) were the substances most frequently used by students since their first year of university, but prescription drugs, especially benzodiazepines (15.4%) and opioid-based drugs (14.7%), were also frequently used; (ii) having already felt dependent was reported by one-third of the students who had used benzodiazepines and methylphenidate, nearly one-quarter of cannabis and cocaine users, approximately 20% of those who had used the opioid-based drugs, modafinil and amphetamines, and by more than 10% of alcohol users; (iii) the reason for use varied depending on the substance considered, with the most common being recreational use; (iv) the lowest score on the self-assessment scales was for the academic situation in comparison with family, social and income situations; and (v) the prevalence of use of certain psychoactive substances varied according to the field of study, with the humanities and social sciences fields representing a risk group for several of the substances evaluated, while students in the health and sport field were the most at risk for nitrous oxide use.

Concerning free-access psychoactive substances, the high prevalence of alcohol and tobacco use is consistent with literature data (Tavolacci et al. 2013; Batisse et al. 2021; Perino et al. 2022). The fact that more than half of the students reported having experienced a feeling of dependence to tobacco is not surprising given the high addictive potential of nicotine (Nutt et al. 2007). However, these data, along with the fact that over 10% of students reported having already felt dependent to alcohol, are worrisome in this young population given the high propensity for these substances to cause illness and death as a result of chronic use (Nutt et al. 2007). We found that 6.8% of the respondents reported nitrous oxide use since first entering university. Even if only a few described already feeling dependent or having a regular frequency of consumption, nitrous oxide use is still a source of concern. This substance, also called a laughing gas, for a long time has been considered as harmless. Importantly, its use for non-medical purposes has recently increased, raising concerns about risk of accidents, addiction and neurological adverse effects (Fidalgo et al. 2019; Lapeyre-Mestre et al. 2020; Micallef et al. 2021; Largeau et al. 2022). More recently, cases published in the literature have linked the recreational use of nitrous oxide with the occurrence of various thrombotic complications (Oulkadi et al. 2022). Thus, the monitoring of this phenomenon, particularly by addictovigilance systems, remains essential (Lapeyre-Mestre et al. 2020). Although sulbutiamine use was described by few students, 7% of users reported a sense of dependence, highlighting the importance of monitoring the risk of over-the-counter medications. To our knowledge, only few data exist in the literature concerning the risk of misuse and dependence on sulbutiamine (Douzenis et al. 2006).

Concerning the use of prescription drugs, benzodiazepine and opioid drug use were frequently reported by the respondents, which is consistent with previous studies (Batisse et al. 2021; Perino et al. 2022). The fact that more than one-third of benzodiazepine users reported having already felt dependent and that 20% described a consumption rate of every day or almost every day is particularly of concern. Indeed, France is one of the largest consumers of benzodiazepines in the world, and their chronic use could lead to undesirable effects such as deleterious impact on learning outcomes in addition to substance use disorders, drowsiness, falls or hypotension (Bonnay et al. 2021). In our study, the reasons for use were mostly medical treatment (78.3%), other (17.0%), search for a recreational effect (10.3%) and help with concentration (6.7%). The fact that the main reason for use was for medical treatment indicates a significant level of anxiety. This anxiety requiring drug treatment could be related to several factors, including the sanitary context. Indeed, it should be mentioned that this survey took place in the spring of 2021, approximately one year after the beginning of the pandemic. However, we do not have comparative data to assess more precisely the role of the health crisis in the challenges faced by students. These results, in addition to those of the lowest score on the self-assessment scales for the studies situation, seriously question the well-being of students in their academic careers. In addition, students are not always aware of the adverse effects associated with the treatments taken. Here, the risk of short-term memory impairment with benzodiazepines could have an additional deleterious impact on studies. The question of pharmacological management of an identified anxiety must therefore be based on an optimal evaluation of the benefit/risk balance.

A feeling of dependence was also frequently reported by opioid prescription drug users, but the frequency of use was more occasional. However, although the main reason for use was drug treatment, over 10% of users reported recreational use. Furthermore, opioid prescription treatment can also be accompanied by prescription opioid misuse. In a previous study conducted in adults with chronic noncancer pain, the motivations cited for prescription opioid misuse, apart from pain relief, were to calm down, relax and improve mood (Kerckhove et al. 2022). Prescription opioid misuse was shown to be related to the male sex, young age, the presence of nociplastic pain of severe intensity, codeine use and coprescription of benzodiazepines (Kerckhove et al. 2022). Among other complications (Biancuzzi et al. 2022), prescription opioid misuse may lead to increased suicidality (Ashrafioun et al. 2019), and intervention at this level is also essential.

Unlike benzodiazepine and opioid prescription use, methylphenidate and modafinil uses were much less reported by students. Prevalence use was similar to that found in previous French studies (Fond et al. 2016) but much less important than that found in some other countries (Agence Nationale de Sécurité des Médicaments et des Produits de Santé., 2007). This could clearly be related to the strong restrictions on the prescription and delivery of methylphenidate and modafinil in France (Agence Nationale de Sécurité des Médicaments et des Produits de Santé., 2022a; Agence Nationale de Sécurité des Médicaments et des Produits de Santé., 2022b). Only two-thirds of responders described methylphenidate as a medical treatment. The other most frequently reported reasons were improved concentration, alertness and wakefulness. This could be related to addressing undiagnosed or subthreshold ADHD (Hartung et al. 2013) but also, as previously hypothesised, to reinforcing alertness in social situations and therefore facilitating prolonged social engagement (Rabiner et al. 2009). Even if the potential of abuse of methylphenidate has already been described and discussed (Pauly et al. 2019), the fact that more than a third of the users reported having already felt a sense of dependence could also reflect the need to consume a drug treatment to alleviate symptoms rather than represent misuse itself. Indeed, methylphenidate is a pharmacological treatment of adult ADHD (Weibel et al. 2020) that can be taken every day and especially on days when the person needs to concentrate. Interestingly, unlike methylphenidate, which was taken orally by all respondents, cases of misuse of modafinil were described, with intake by injection, sniffing or inhalation. Although piracetam is officially recognised as a nootropic drug (Sharif et al. 2021), with prescribing conditions not as restricted as those for methylphenidate or modafinil, its use was rarely reported by students. It could be linked to the fact that the enhancing effects in the healthy individual’s brain has been described as moderate (Sharif et al. 2021). However, its potential for misuse was highlighted in our study, with several students describing a use for experimentation and a use by smoking, injecting or snorting.

Concerning the use of illegal drugs, the high prevalence of cannabis misuse in the student population is consistent with previous studies (Batisse et al. 2021; Perino et al. 2022). Associated with the fact that a quarter of students described having experienced a feeling of dependence and 10% report daily consumption is worrisome given the risk of psychiatric and cardiovascular complications (Jouanjus et al. 2017; Gukasyan and Strain 2020). The prevalence of illicit psychostimulants like cocaine, amphetamine, and MDMA, was similar or slightly higher than in previous French studies (Fond et al. 2016; Batisse et al. 2021; Perino et al. 2022), but lower than in countries like the United States of America (13%) (Kasperski et al. 2011) and higher than in countries like the Netherlands (1.3%) (Schelle et al. 2015). Notably, in our study, approximately 20% of cocaine and amphetamines users described having experienced a feeling of dependence. Although use for experimental or recreational purposes was most frequently reported, uses to improve concentration, alertness and vigilance were also frequently described, which raises the question of cognitive doping (Hildt et al. 2015). The fact that improvement of sexual abilities was also described as a reason to consume cocaine, amphetamine or methamphetamine raises the issue of chemsex, i.e., the use of psychoactive substance to initiate, facilitate, improve and prolong sexual experiences, which has been described as highly prevalent in students in a recent study (Malandain et al. 2021). Improving sexual performance was also a reported reason for using NPS, heroin and LSD, with injectable routes used for NPS and heroin, suggesting slamming practices. Slamming consists of injecting psychostimulants (including NPS) intravenously to increase sexual performance. Although the use of these substances was not frequently reported, chemsex practices expose students to complications such as substance use disorders, acute neurological or cardiovascular intoxications, various psychiatric disorders, and viral and bacterial infections (Malandain et al. 2021; Batisse et al. 2022). Finally, it’s worth noting that although heroin was the substance least reported by students, it seemed to be the most addictive after tobacco.

Interestingly, we found that substance use since first entering university differed according to the field of the study. The fact that nitrous oxide use was more frequent in students in the health and sport field is consistent with the historical use of this substance in medical settings. However, it also shows that the toxicity of the product remains underestimated in a population normally more experienced in the evaluation of drug adverse effects. The fact that students in the social sciences field (including human and social sciences + art, literature and language) represent in our study a risk group for several of the substances evaluated also makes it a particular target for prevention.

We should acknowledge several limitations to this study. First, the response rate was 6.1%, which may have led to a selection bias. Second, the monocentric character limits its extrapolation. Third, although the predominantly female sex ratio of study respondents was consistent with the sex ratio of all students enrolled at the university (61%, see Supplemental Data) (Université de Lille 2021), this may have led to a biased estimation of substance use, as substance use disorders affect women and men differently (Fonseca et al. 2021). This overrepresentation of women is not surprising as previous studies have found that women were more likely to participate in scientific studies than men (Galea and Tracy 2007; Wathelet et al. 2020). Fourth, given that the study is based on a self-questionnaire, information and participation biases cannot be excluded and may have led to an over- or underestimation of the reported consumption. At last, as this cross-sectional study was the first one conducted in this population, we do not have data allowing us to compare the use of psychoactive substances before and after the health crisis.

Our study allowed us to take a picture of psychotropic drug use in a student population, underlining the importance of the addictive problem in this population and the interest in targeted prevention measures according to the substance and the field of study. More specifically, prevention measures should focus on alcohol, cannabis, illicit psychostimulant drugs, nitrous oxide, and prescription drugs (benzodiazepines, opioids) use among university students. An extension of this study to other centres is planned to increase the power and to establish comparative analyses between universities. It is a tool that will allow to follow the consumption of substances according to the general and sociological contexts but also to evaluate the impact of prevention and support policies on the consumption of psychoactive substances.