This study describes the characteristics of participants reporting dependence and/or abuse versus those reporting simple use of PAS 1 week prior to incarceration and the evolution in the trend of use between 2013 and 2022. A previous study over the period 2003–2006 used the same program in jails compared to subjects included in other structures of care [8]. Results showed that prison inmates are younger and present worse social‐economical indicators and consume more products, more illicit ones and more benzodiazepines such as flunitrazepam and clonazepam prior to imprisonment. If we compare the overall consumption data of our population with that of this previous study, we can note a lower consumption of cocaine/crack (19.6% versus 28.6%), and benzodiazepines (15.5% versus 23.1%), but a comparable level of heroin consumption (10% versus 14.8%) [8]. Despite an abundance of research on substance abuse and dependence within prison populations in France, there remains a critical gap in understanding how specific prison inmates' characteristics are associated with these issues. This lack of targeted studies hinders our ability to tailor interventions effectively, emphasising the need for more nuanced investigations into these relationships.

Yet, in our study, we aimed to evaluate the association of participant characteristics with simple use or abuse/dependence to advocate for evidence‐based abuse/dependence treatment of adults in a prison setting. We found that 85.5% of participants reported abusing/being dependent on at least one substance, which is much higher than the prevalence of substance use assessed in another French study among men prison inmates (28.7%) compared to the general population (5%) [13].

Results showed that higher rates of abuse and dependence were seen among men in comparison to women, as part of our study findings. These results should be treated with caution given the low representation of women in our study (8.4%); the prisons included were predominantly male establishments. However, this percentage is comparable to European data, which estimates the representation of women in European prisons at 5% [1]. However, research has frequently identified key differences in SUDs between males and females [14, 15] and similar results were identified in another published paper, which demonstrated that male sex was a predictor of SUD [16].

When assessing reported substances by participants, cannabis was the most reported substance over the period of our study, followed by cocaine, benzodiazepines and then heroin. Comparable prevalences were found in another study carried out in the prisons of a single region in France among 800 prison inmates, the week preceding incarceration (as in our study): cannabis (49%), cocaine (16.5%), heroin (8.9%) and benzodiazepines (15.9%) [17]. This is the same for another study carried out among Belgian prison inmates with a prevalence of use before incarceration of 40.9% for cannabis (versus 52.8% in our study), 27.5% for cocaine/crack, 13.6% for heroin and 12.2% for benzodiazepines [5]. The consumption of benzodiazepines is higher in our study (23.1%) compared to all these other studies. The use of benzodiazepines is widely prevalent in France, even as this has decreased in recent years within the general population [18]. In subjects with SUD, benzodiazepines may be used to manage withdrawal symptoms from other substances (opioids, alcohol) or anxiety‐inducing effects after stimulant use. However, the percentage of benzodiazepine consumption in this population is comparable to that found in all subjects included in the OPPIDUM survey where the use of benzodiazepines has been around 20% for several years [7, 19]. For other substances, consumption levels are comparable to those of the entire OPPIDUM survey except for cannabis, which is much higher in the population in prisons (52.8% versus 36%) [19].

In the general European population, cannabis and cocaine are the two most used illicit substances [20]. It therefore seems consistent that these three substances (cannabis, cocaine, benzodiazepines) occupy a predominant place in preincarceration use by the subjects in our study. In a recent French study, 25% of prison inmates consumed cannabis either daily or regularly (at least 10 times a month) before their incarceration [6]. Moreover, in the United States of America, cannabis was also stated as the main substance taken preincarceration in another study where 89% of the participants who reportedly consumed PAS over the previous 6 months used cannabis followed by cocaine or powder crack (11%) and heroin (8%), as reflected in our results [21]. In addition, both cocaine and opioids including heroin were reported by other mentioned studies in prisons [22]. Comparable results showed that the highest rates of use are reported for cannabis, cocaine and amphetamines, and to a lower extent heroin and other types of drugs [23].

Similarly, prison inmates report high levels of lifetime prevalence of substance use before imprisonment and increased levels of consumption, especially of heroin, cocaine and amphetamines, compared with the general population [1]. Moreover, a greater rate of participants in the group abuse and dependence also stated a history of polysubstance use, comparable to the results presented by other studies inside and outside prison settings [24].

By contrast, several variables were identified in the final model of the multivariate analysis illustrating a significant association with abuse/dependence versus simple use. Although alcohol dependence was not identified in our final model of the multivariate analysis, bivariate analysis indicated a higher rate of abuse and dependence among participants with a reported history of alcohol dependence. These results were also noted in other studies suggesting that tobacco use and relapse are largely connected with a hazardous pattern of alcohol use rather than with moderate drinking [25]. Similarly, it was stated in the literature that smoking often occurs in combination with the use of other PAS and cigarettes may become a trigger for using illicit drugs [26]. At the same time, data from 50 countries, which represent 73.5% of all prison inmates in the world, conveyed that smoking by this particular population exceeded community rates 1.04‐ to 62.6‐fold [27].

Notably, the strongest and most significant association among substances reported by participants was observed with heroin or speedball use, followed by cocaine or crack. Cannabis and benzodiazepines showed comparatively lower odds of dependence and abuse. Several studies have compared the reinforcing effects of the coadministration of cocaine and heroin, referred to commonly as “speedball”, to either drug alone [28]. The reinforcing effects of substances like heroin, cocaine and their combination (speedball), are pharmacologically driven by how these drugs interact with the brain's reward and neurotransmitter systems [29, 30]. Heroin dependence is strongly linked to its pharmacological action on opioid receptors, with active metabolites like morphine and morphine‐6‐O‐glucuronide contributing to acute effects, tolerance, physical dependence and addiction development, underlying its high addictive potential [31, 32].

Injected drug use also was shown to raise the odds of abuse and dependence approximately four and a half times higher among subjects compared to simple use; this was further noted by other studies reporting that smoking a drug or injecting it increases its addictive potential [33, 34].

A critical finding from our statistical model was the lower odds of abuse and dependence among participants on substitution treatment, showing the OST protective effect on the risk of abuse and dependence; they had 50% lower odds of abuse and dependence compared to those who were not. Substitution treatment programmes have the greatest potential to reduce injecting drug use and the resulting risk of the spread of infection [35]. Thus, providing both drug dependence treatment and harm reduction schemes in prison is therefore essential [35]. A recent study in Australia demonstrated that upon entry to prison, injecting drug use decreased but syringe sharing increased among injectors [36]. Furthermore, the provision of OST in prison is associated with a reduced prevalence of injecting drug use in prison among people with a long‐term history of intravenous drug use [37], as well as being an opportunity to engage in drug treatment in one of the highest risk and hard‐to‐reach groups [38].

To our knowledge, this is the first study to explore the association of demographic factors, history of substance use, addictive behaviour and substance use among the recently incarcerated in France. It is also the first large‐scale study to estimate the prevalence of abuse or dependence among prison inmates over an 11 ‐year period between 2013 and 2022.