In recent years, there has been an increase in the intentional use of drugs for sex, which can last for hours or even days, among men who have sex with men (MSM) (1–6). The recreational uses of substances vary in place or environment. Some of these recreational consumptions take place in sexual environments, a term known in Europe as sexualized substance use, where we include “Chemsex” linked to the LGTBIQ+ sexual culture (7). However, we find other denominations in the world, such as “Intensive sex partying” in Australia (8), “Party and Play” (PnP) in North America, or even “sexualized drugs” used more in the general population (9). This shows that it is a global problem present at the international level.

The Chemsex phenomenon has been linked to risky sexual behaviors, as well as an increase in sexually transmitted infections (1, 10–13). According to the latest European online survey for MSM (EMIS - 2017), the section on substance use revealed the prevalence of substance use for sexual purposes in the last 12 months was 14.1% (14, 15), with Spain being one of the countries with the highest prevalence of chemsex at the European level (16, 17). The substances most commonly used in the practice of Chemsex include methamphetamine, mephedrone, and other synthetic cathinones, gamma-hydroxybutyric acid/gamma-butyrolactone (GHB/GBL) (1, 2, 9, 14, 15, 18–26) alkyl nitrites (poppers) (27) medication for erectile dysfunction (6, 28–30) and less frequently other substances such as cocaine and ketamine (13, 22, 31). If the consumption of these psychoactive substances is intravenous (19, 32) in this context, it is called slamming or slamsex (1, 6, 14, 25, 28, 29).

Several sexual practices have been described in context of chemsex, such as unprotected anal intercourse or “bareback” (33, 34) “fist-fucking” (19, 32, 33, 35) group sex (33) which have been associated with an increased risk of being diagnosed with sexually transmitted infections (STIs) such as gonorrhea, chlamydia, syphilis (6, 11, 18, 21, 23–27, 29, 32, 35–38), hepatitis C (HCV) and HIV (15, 19, 22, 30, 39). For this reason, chemsex is considered a health concern due to the increase in HIV primary infection, hepatitis C reinfections (14), and, in general, a higher probability of acquiring sexually transmitted diseases (STDs) (1, 14, 23). A higher incidence has been observed in PLHIV (People living with HIV) versus MSM who do not have HIV (15, 25). As a consequence, PLHIV are at increased risk for mental health problems (6, 25, 32, 34), specifically anxiety and depression (23, 36). In the same vein, Chemsex practices have been associated with increased risk of psychosis (6, 14) and delusional thoughts due to chronic methamphetamine use (29, 40), suicidal ideation (6, 41) anxiety, depression (14, 34), overdose (15), behavioral disturbances (6), substance addiction (26) and reduced adherence to PrEP treatment (6).

The reasons why MSM engage in chemsex can be diverse, including increasing libido (27), intensifying sexual pleasure (18), facilitating sexual euphoria and disinhibition (39), better management of negative emotions such as lack of self-confidence during sex (14,40.43), improved perceived quality of sex and relationship with internalized homophobia (14), prolonged duration of sex sessions (1) and realization of sexual fantasies.

Furthermore, the rapid changes in substance consumption, including the expansion of new psychoactive substances (NPS) reported in Europe (42), underscore the need to explore the profile of substance consumption in sexual contexts among MSM. Understanding these profiles could provide insights into the possible connection between chemsex and MSM participation in these practices, particularly in light of the association between chemsex and sexually transmitted infections (STIs), as well as the emergence of antibiotic-resistant infections.

Our research aimed to explore the profile of men who have sex with men in a sexual context since it could explain the relationship between chemsex, sexual behavior, and the increase in the diagnosis of STIs. The profile of users who practice chemsex is that of a man between 18 and 55 years old, resident in Spain, with university studies and a permanent job. Previous research has indicated that individuals aged between 36 and 45 years old are more inclined to engage in chemsex compared to other age groups (44). These findings align with our study, where the average age of substance use and participation in chemsex was 36 years old.

Our research concludes that being a young man, living in large cities, and being exposed to environmental stressors and substance use in the last 12 months may be additional risk factors associated with a high prevalence of chemsex. These factors are in line with other studies that have scientifically established that the homosexual population is potentially up to twice as prone to experiencing psychotic symptoms compared to the heterosexual population (45, 46). Chemsex has been identified as a coping mechanism for the stressors that men who have sex with men (MSM) encounter regularly (45, 47).

The research presents an alarming picture of the prevalence of sexually transmitted infections (STIs) among men who have sex with men (MSM) involved in chemsex and slamsex. According to the study data, 17.94% (n = 101) of the participants reported being diagnosed with any STI in the last 6 months, data that is consistent with other studies (15, 30). An important finding of our research and worth noting is that 21% of the sample was on treatment with pre-exposure prophylaxis (PrEP), observing a strong association between being on treatment with PrEP and the diagnosis of gonorrhea, chlamydia, genital herpes, and syphilis, which also confirms the results of similar studies (35, 48).

This is striking, as one might expect those on PrEP to be less exposed to STIs due to their greater awareness of sexual health and regular intake of preventive medication. However, the results show that, among participants on PrEP, there were higher rates of diagnosed STIs: 29.16% for gonorrhea, 23.33% for chlamydia, 8.33% for genital herpes, and 17.5% for syphilis. In comparison, those who were not on PrEP also had a significant prevalence of STIs, but to a lesser extent: 7.44% for gonorrhea, 5.64% for chlamydia, 3.38% for genital herpes, and 5.41% for syphilis. Thus, there is an increasing trend among MSM in treatment with PrEP who practice chemsex with higher rates of STI diagnoses (18, 29, 32, 35–37, 48–50). For all of the above, harm reduction strategies and community-based chemsex approaches that combine support services with health promotion and education activities should be pursued (51–53). Given the entry of PrEP into the service portfolio of the National Health System (SNS), the Secretariat of the National AIDS Plan (SPNS) launched the SIPrEP in 2020, an information and monitoring system for the implementation. Running and implementation in the different Autonomous Communities (CCAA) of the PrEP programs, with the aim of collecting information on the number of participants, their characteristics, their clinical evolution and the effectiveness of PrEP. Thus, up to and including 2023, the estimated number of users who were taking PrEP is 18,075 people (54).

On the other hand, substance use appears to be associated with an increased risk of STIs in general. MSM who engage in chemsex have been reported to be at increased risk of transmitting STIs and at increased risk of engaging in risky sexual behaviors, and acquiring HIV (55). People who use amyl nitrite, GHB/GBL, alcohol, ecstasy, amphetamines, ketamine, methamphetamine, mephedrone, and cocaine have a higher proportion of STIs compared to those who do not use these substances. When considering substance use in the context of chemsex and slamsex, the results show a significant association between the use of certain substances and the prevalence of STIs. For example, 39.8% of GHB/GBL users had STIs compared to 18.93% of non-users, suggesting that the use of these substances is associated with an increased risk of STIs. Data that are also consistent with other studies in which drugs used in the chemsex context were related to STIs and sexual risk behaviors (30, 56–61). Moreover, the findings of a previous study demonstrated a 2.83-fold increase in the likelihood of acquiring a sexually transmitted infection (STI) among chemsex users (30). This result aligns with the outcomes of the current study.

These data reinforce the need for continued sexual health education and safer practices, even among those on PrEP. The high prevalence of STIs among participants on PrEP suggests that access to preventive medication is not sufficient to eliminate STI risk and that other factors, such as sexual risk behavior, may be at play.

In regards to slamsex, it is notable that a significant percentage of participants in our study reported consuming injected substances (14.7%) in the past year compared to those who did not inject drugs. Among individuals who engaged in slamsex, a higher frequency of STI diagnoses was observed, consistent with findings from other studies. For instance, research has shown that 15.7% of individuals who practiced slamsex in the previous year reported a higher frequency of STI diagnoses and engaged in high-risk sexual behaviors (29). Other studies focused on drug use and STI risk have shown an increased risk of STI acquisition by people who use drugs (39), which may be related to the search for new sensations and experiences as well as disinhibition. Risk behaviors associated with chemsex, such as having multiple sexual partners, having unprotected sex, engaging in fisting and slamsex, as well as sharing injection equipment, may be risk factors for acquiring STIs in the past 6 months in the context of chemsex (29, 36, 45).

Along the same lines, the most commonly consumed injecting drugs during slamsex associated with STI diagnosis in our study were ketamine (75%), followed by mephedrone (65.4%), and methamphetamine (57.1%). The potent stimulant effect of mephedrone has been associated with a heightened risk of engaging in high-risk sexual behaviors, which in turn increases the risk of HIV infection and other sexually transmitted infections (STIs) (62). Additionally, mephedrone use has been linked to severe psychiatric symptoms, intoxications, and dependence on injecting drugs (29). This includes a range of adverse effects such as binge drinking, anxiety, binge eating, withdrawal symptoms, and psychotic symptomatology resulting from injecting mephedrone use (6, 29, 63).

The significant prevalence of substance use within the context of chemsex, coupled with its correlation with risky sexual behaviors, underscores the importance of targeting men who have sex with men (MSM) as a critical population for prevention strategies. These findings support the need for comprehensive interventions that address both substance use and sexual health to reduce STI risk in vulnerable populations, especially in populations where chemsex is prevalent, as appears to be the case in Spain and who are on PrEP treatment. Addressing chemsex can yield broader positive impacts on individuals’ mental, sexual, social, financial, and overall health. A retrospective case review conducted in a London service found that half of MSM who reported engaging in chemsex perceived subsequent adverse physical and mental health consequences, highlighting the need for comprehensive support and intervention strategies (32, 64).

Furthermore, there exists an association between engaging in chemsex and the heightened risk of experiencing emotional instability, including symptoms of anxiety and depression. These findings align with numerous previous studies conducted among MSM, which have consistently reported a link between drug use for sexual purposes and an increased likelihood of experiencing depressive outcomes (39). Indeed, some studies have identified anxiety as a predictor in the relationship between psychosis and chemsex (29). Conversely, other research has found no significant differences in anxiety levels, although it did reveal that chemsex users exhibited higher scores on the GAD-7 scale (34). This may suggest that the use of substances to extend time in a sexual context may provoke depressive symptoms with ideas of guilt and ruin of the people who practice it, or also, it may be depressive symptoms such as social isolation and loneliness that lead to substance use in a sexual context to disinhibit themselves and be a way to socialize with other people. Our findings also suggest that risk factors such as substance use, poly consumption, engaging in slamsex, and injecting methamphetamine use are associated with an elevated likelihood of experiencing a psychotic break. This association with the risk of psychosis aligns with the results of previously published studies (29, 45).

Associations have been noted between chemsex and an increased risk of suicide. Additionally, there is evidence of an association between chemsex, impulsivity, and distorted body perception. A recent meta-analysis conducted in Sweden (65) reported a suicide attempt rate of 10% in gay men compared to 2.2% in heterosexual men. This suggests that MSM and individuals involved in chemsex may have a higher lifetime risk of suicide attempts compared to the general population (34).

One of the strengths of our study is that the survey was anonymous, so participants may be especially willing to disclose their chemsex experiences. Other strengths of our study are validated measurement methods, multivariate analysis, and explicit questions about chemsex.

Our findings have certain limitations. Using a cross-sectional study design means that the relationships between variables cannot be interpreted as cause-and-effect. Additionally, the use of non-probability purposive sampling to obtain the sample restricts the generalizability of our results to the broader MSM population. However, the sizable sample size suggests that the results hold validity. Since this is a self-administered survey, the results reflect the respondents’ viewpoints, which may not fully represent the clinical experience. Furthermore, variations in participants’ roles may have influenced their knowledge, experiences, and perceptions of the chemsex phenomenon.

The study highlights the high prevalence of “chemsex” among men who have sex with men (MSM), increasing the risk of STIs. It underlines the urgent need for preventive strategies and care programs tailored to this population. Chemsex poses unique public health challenges, requiring a comprehensive approach that addresses substance use and sexual health. Individuals involved exhibit high-risk behaviors, along with symptoms of psychopathology and substance dependence. Therefore, identification, education and prevention programs are crucial to mitigate negative consequences. Improving awareness of PrEP as HIV prevention can be effective, as can screening programs for health problems related to drug use, and interventions to increase awareness of risks and provide access to health resources.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by the Committee of the University of La Rioja with verification code (CSV) (D2R1m2Iu3vLVPdIzGZVVnK0h6N558tCyN). The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

PP-H: Writing – review & editing, Writing – original draft, Methodology, Conceptualization. EB-G: Writing – review & editing, Writing – original draft, Supervision, Conceptualization. AM-S: Writing – original draft, Methodology, Investigation, Data curation, Conceptualization. EC-S: Writing – original draft, Supervision, Software, Methodology, Formal analysis, Conceptualization. VG-C: Writing – original draft, Visualization, Validation, Resources, Project administration, Funding acquisition, Formal analysis. JC-R: Writing – original draft, Methodology, Formal analysis. MC: Writing – original draft, Methodology, Investigation, Conceptualization. PK: Writing – original draft. JM-T: Writing – original draft, Resources, Project administration, Methodology, Investigation. MS-B: Writing – original draft, Project administration, Formal analysis. RV: Writing – original draft, Visualization, Validation, Software, Resources, Project administration, Investigation, Funding acquisition, Formal analysis. RJ-V: Writing – review & editing, Writing – original draft, Supervision, Methodology, Investigation, Funding acquisition, Formal analysis, Conceptualization.