Background

In December 2021, approximately 11.5 million people were incarcerated globally, with 70% in low and middle-income countries [1]. Iran, ranking 10th globally with around 180,000 incarcerated individuals in 2023 [2], faces notable health challenges among its prison population. Infectious diseases are particularly prevalent, with high rates of tuberculosis (62.6%), HIV (2.8%), HCV (21.6%), and HBV (2.9%) [3]. These health issues are primarily attributed to high-risk behaviors common among incarcerated individuals in Iran, both before and during imprisonment. Such behaviors include unprotected sex, alcohol consumption [4, 5], and drug use, both through injection and non-injection methods [6, 7].

The intersection of incarceration, health risks inside the prisons, and drug use is a critical public health concern in Iran [6, 8]. The concentration of individuals in prison presents challenges in managing health risks and addressing drug-related concerns. [9, 10]. Despite several policies and interventions to prevent drug trafficking into the prisons, illegal drugs enter prisons through various ways (e.g., visiting relatives, prison staff, newcomers, and postal gifts) [9]. Legal obstacles and limitations in the prisons for drug use shape a condition in which the risk of high-risk behaviors increases. For example, the results of a former study have shown that 67% of people who inject drugs had a history of shared injection, and 19% of the shared injection occurred inside prison [11]. In a more recent study, it was found that 3.8% of incarcerated individuals had a history of shared injection [12]. For many incarcerated people, prisons are one of the first opportunities to engage in risky behaviors, including drug use [13].

Since the onset of the HIV outbreaks inside Iranian prisons a few decades ago, Iran has implemented extensive harm reduction services, including needle and syringe programs, opioid agonist therapy (OAT), and educational initiatives within its prison system [14, 15]. However, drug use inside prisons in Iran continues to be common with an estimated pooled prevalence of lifetime non-injection and injection drug use of 73.8% (95% CI 70.9, 76.6) and 16.0% (95% CI 12.6, 19.7), respectively [16]. In a separate study conducted among incarcerated individuals in Iran, 70.6% of participants reported drug use, with 10.6% specifically reporting injection drug use [12]. Another study indicated that 74.0% of participants reported drug use, with 12.3% reporting injection drug use [17]. Non-injection drug use inside prisons is a significant concern due to its potential progression to injection drug use and other high-risk behaviors inside and outside prisons [18]. Moreover, developing effective harm reduction strategies within prison settings in Iran requires a nuanced understanding of non-injection drug use. However, there is a scarcity of studies focusing on non-injection drug use among incarcerated individuals in Iran and therefore, this study seeks to address this gap by investigating the prevalence, trends, and associated factors of non-injection drug use among this key population in Iran.

Methods

Three national bio-behavioral surveillance surveys (BBSS) were conducted among incarcerated people in Iran in 2009, 2013, and 2017 to help monitor the trend of HIV and high-risk behaviors among incarcerated people in Iran. The study design and implementation details have been previously described [4]. We collected data from 27 prisons in 2009, 27 prisons in 2013, and 33 prisons in 2017 representing different geographical regions of Iran [19]. The median number of incarcerated people was used as a cutoff to divide prisons into two categories: Prisons with more than the median and less than the median. Overall, using a multi-stage random sampling method, in 2009, 5953 participants, in 2013, 5490 participants, and in 2017, 5785 participants were recruited. Eligible participants were ≥ 18 years old, had been incarcerated for at least one week at the time of the study, and provided informed consent for participation. Gender-matched interviews were conducted in a private room inside the prison facilities. Standard questionnaires were used to assess HIV-related high-risk behaviors (e.g., history of sexual contacts and drug use-related behaviors) and all participants were tested for HIV by a rapid HIV test (SD-Bioline, South Korea). Those with reactive results in the first test were confirmed with a Unigold HIV rapid test. These surveys were supported by the global fund (in 2009 and 2013) and the Ministry of Health and Medical Education (in 2013 and 2017).

Outcome variable

The outcome variable of interest in this analysis was self-reported non-injection drug use inside the prison in the last month. We asked the participants, “Have you used non-injection drugs inside the prison in the last month?” with the binary answers of “yes” vs. “no”.

Covariates

The covariates included demographic factors containing sex (male vs. female), age at interview (18–29 vs. 30–40 vs. >40), educational level (< high school vs. ≥high school), and current marital status (single vs. divorce/widowed vs. married). Other covariates included history of previous incarceration (yes vs. no), length of previous incarceration (≤ 3 vs. 4–11 vs. 12–36 vs. <36 months), duration of non-injection drug use (< 5 years vs. ≥5 years), history of drug use in the last month before incarceration (yes vs. no), type of drug use in the last month before incarceration [opioids vs. stimulants vs. others (including marijuana, ecstasy, tramadol, and other drugs )], receipt of OAT inside the prison (yes vs. no), age at first sexual intercourse (< 18 vs. ≥18 years), using condom during last sex (yes vs. no). We also recorded the history of HIV testing (ever vs. never), HIV knowledge about the modes of transmission (sufficient vs. insufficient) about the modes of transmission [20], and HIV serostatus (positive vs. negative).

Statistical analysis

After merging data from the three rounds, descriptive statistics were reported for drug use in the last month inside the prison, including frequencies, percentages, and 95% confidence intervals (CI). We used a bivariable logistic regression to identify associated covariates and included the covariates with p-value < 0.2 in the multivariable logistic regression model. The model was reduced through a backward elimination [21]. We used a multivariable logistic regression model to compare the odds of drug use in the last month of incarceration among different subgroups of incarcerated people after merging the data from three rounds of surveys and adjusting for the year of data collection. Adjusted odds ratios (aOR) were reported, and p-values < 0.05 were considered statistically significant.

Results

Of all invited participants, 25 people (0.4%) in 2009, 22 persons (0.4%) in 2013, and 15 persons (0.2%) in 2017 denied taking part in studies. Among the 17,228 participants recruited from three rounds, the mean (standard deviation [SD]) age was 34.4 (9.6) (32.2 in 2009, 35.4 in 2013, 35.7 in 2017), 96.0% were male (96% in 2009, 98.1% in 2013, 93.9% in 2017), and 55.3% had a previous history of incarceration (47.4% in 2009, 59.4% in 2013, 59.1% in 2017).

Prevalence of drug use inside prison

Among 17,228 included individuals, 4,153 incarcerated individuals 24.1% (95% CI 23.5, 24.7) (39.7% in 2009, 17.8% of participants in 2013, and 14.0% of participants in 2017) had a history of non-injection drug use in the last month inside prison (Fig. 1). Among those who used drugs for five years or more, 3,652 individuals (32.4; 95% CI 31.5, 33.2) reported using drugs inside the prison in the last month (88.5% in 2009, 93.2% in 2013, and 93.9% in 2017) (Table 1). Furthermore, 55 participants (0.3%) [33 (0.5%) in 2009, 19 (0.3%) in 2013, and 3 (0.1%) in 2017] had a history of drug injection in the last month inside the prison. We also noted that the prevalence of OAT uptake has increased over time (Fig. 2). Additionally, 75.1% of the participants who were on OAT reported stimulant use in the last month inside the prison (See supplementary file).

Fig. 1
figure 1

Prevalence of non-injection drug using inside prison in last month in national bio-behavioral surveillance surveys

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Table 1 Drug use inside the prison in the last month among incarcerated people in Iran in 2009, 2013, and 2017
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Fig. 2
figure 2

Non-injection drug use and opioid agonist therapy (OAT) inside prison in last month in national bio-behavioral surveillance surveys

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Bivariable regression model

From demographic covariates, male sex (Crude odds ratio [cOR] = 3.18, < 0.001), and less than high school education (cOR = 1.33, < 0.001) were significantly associated with non-injection drug use inside the prison. Also, having a history of previous incarceration (cOR = 1.25, < 0.001), condom-less sex in the last sexual act (cOR = 1.54, < 0.001), and having a history of HIV testing (cOR = 1.11, < 0.001) were associated with drug use in the last month inside the prison (Table 2).

Table 2 Bivariable model of non-injection drug use inside a prison in the last month among incarcerated people in Iran in 2009, 2013, and 2017
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Multivariable logistic regression model

In the multivariable logistic regression model, the year of interview [2013: aOR = 1.43; 95% CI 1.25, 1.63 and 2009: aOR = 5.60; 95% CI 4.90, 6.41], younger age [19–29: aOR = 1.14; 95% CI 1.02, 1.29 and 30–40: aOR = 1.37; 95% CI 1.23, 1.54)], male sex [aOR = 3.35; 95% CI 2.49, 4.49], < high school education [aOR = 1.31; 95% CI 1.19, 1.45], having a history of previous incarceration [aOR = 1.26; 95% CI 1.16, 1.38], and having a history of HIV testing [aOR = 1.76; 95% CI 1.60, 1.94] were positively and significantly associated with drug use in the last month inside the prison (Table 3).

Table 3 Multivariable logistic regression on non-injection drug use inside the prisons in the last month among incarcerated people in Iran in 2009, 2013, and 2017
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Discussion

In our analysis of data gathered through three rounds of the BBSS conducted among incarcerated people in Iran, we found that despite a decline in reported drug use from 2009 to 2017, approximately one in four participants still reported non-injection drug use within prison during the month preceding the survey. Male sex, younger age, low education, history of previous incarceration, and history of HIV testing were significantly and positively associated with drug use. The prevalence of injection drug use was approximately 3 per 1,000 incarcerated individuals, also exhibiting a decreasing trend from 2010 to 2017. This low prevalence and downward trajectory suggest that the implementation of harm reduction services may have been effective, facilitating a transition towards lower-risk drug-use practices among the prison population.

About 25% of the incarcerated people in the surveys reported using drugs inside the prison within the last month. A few studies have provided insights into the prevalence of drug use within correctional facilities in different countries. For example, in Spain, the prevalence of drug use inside the prison in the past six months among women was reported as 52% [22]. A study in Ghana reported a drug use prevalence of 25.3% in the last month inside the prison [23]. The variability in drug use prevalence across these studies likely reflects the complex interplay of factors influencing substance use in correctional settings. Cultural differences, divergent national drug policies, and variations in prison management strategies may all contribute to these differences [24]. Despite existing services inside Iranian prisons, the uptake of harm reduction programs remains suboptimal. To address this, a multi-faceted approach is needed. Implementing comprehensive screening upon entry can help identify high-risk groups, allowing for more targeted interventions. These interventions should include expanding harm reduction programs, improving access to OAT, and offering educational and supportive programs. To increase the uptake of these services, prisons can employ various strategies. Internal advertising campaigns can raise awareness about available programs. Additionally, implementing behavioral counseling sessions can help motivate incarcerated individuals to engage with these interventions. By combining improved access with increased awareness and motivation, prisons can potentially reduce drug use-related harms more effectively. At a more structural and upstream level, ending the war on drugs is imperative, particularly in Iran, where over 80,000 incarcerations are attributed to drug-related charges [25]. Shifting from punitive measures to a public health approach would enable evidence-based harm reduction in prisons, fostering rehabilitation, reducing recidivism, and addressing the root causes of substance use more effectively [26, 27].

Our study findings indicate that the prevalence of OAT uptake within prisons has shown a consistent upward trend from 2010 to 2017. While this is encouraging, it is important to note that concurrent OAT uptake and drug use remain high and have shown an increasing trend from 2013 to 2017. In 2017, a striking three-fourths of participants receiving OAT reported concurrent stimulant use inside prison. This finding highlights a critical gap in the harm reduction programs currently implemented inside Iranian prisons. While existing programs primarily focus on opioid use, with the government mandated to provide methadone for incarcerated individuals who use drugs [28], the issue of stimulant use remains largely overlooked. This oversight is significant, as there are currently no specific interventions tailored for those who use stimulants in Iranian prisons. The lack of comprehensive drug treatment programs that address both opioid and stimulant use may explain why many participants continue to use drugs despite having access to OAT. Due to the high prevalence of stimulant use among the incarcerated people in Iran, specified drug use in a range of psychosocial (e.g., matrix model [29], cognitive-behavioral therapy, contingency management), and pharmacological treatments (e.g., monoamine agonists and dopamine agonists [30]) for stimulant use disorders should be introduced in the mental health care packages presented inside prisons. By broadening the scope of interventions, Iranian prisons can better support the health and well-being of incarcerated individuals struggling with various forms of substance use.

Previous history of incarceration was an indicator that an individual may engage in drug use while in prison. This association may arise from the fact that repeated or extended periods of incarceration are linked to risk factors associated with drug use [9]. Moreover, people with a history of incarceration often face difficulties, such as limited access to social support and increased susceptibility to exposure to risky behaviors [31]. In our study, over half of the incarcerated people had a history of previous incarceration, and a majority of them had a history of drug use inside the prison. Other studies have also shown similar results [9]; 53.8% of participants in a national study in Iran [9], and 41.0% of participants in a study in Pakistan had a previous history of incarceration which was a significant risk factor for drug use [32]. Evidence shows many people experience drug use for the first time inside prison [9, 33], potentially contributing to higher rates of substance use within prisons compared to the general population. According to recent studies, opium is the most prevalent drug in Iran with an estimation of 1500 per 100,000 population followed by shire (660 per 100,000), crystal methamphetamine (590 per 100,000), hashish (470 per 100,000), heroin/crack (350 per 100,000), methamphetamine, LSD and ecstasy (300 per 100,000) and injecting drugs (280 per 100,000) [34]. Some studies have shown that incarceration can increase drug use inside prison for those who are already vulnerable to a broad range of social stresses [33]. This vulnerability, combined with the prison environment, may increase the likelihood of drug use initiation or continuation. Furthermore, repeated incarcerations may escalate the probability of drug use, creating a cycle that is difficult to break. Connecting incarcerated people with support networks and community-based drug treatment services before release can significantly reduce post-incarceration drug use and risky behaviors. By providing continuous support from prison to community, these connections address key factors contributing to recidivism, such as housing, employment, and ongoing treatment needs [35, 36]. This strategy helps maintain progress made during incarceration and supports a smoother transition back into society. Accessing support networks or social networks, and connecting incarcerated individuals with community-based drug use treatment and support services after prison can reduce risky behaviors and their tendency to use drugs after being released. This approach can facilitate reintegration into society and reduce the likelihood of reoffending.

Limitations

We acknowledge the limitations of our study. First, it was a repeated cross-sectional study, so we could not find evidence of a temporal and causal relationship between the variables. Second, using self-report as the method of data collection can cause underestimation, and participants may not answer our questions correctly for various reasons which could result in information bias. To reduce this bias, gender-matched interviewers conducted face-to-face interviews in a private room inside the prison and we assured the participants that the questionnaires were anonymous. Third, recall bias was unavoidable because some of the questions required participants to remember old information. To reduce this bias, the recent behaviors were assessed during the interview. Fourth, Due to the anonymous nature of the questionnaires and the absence of recorded identification by the study team, it is not possible to determine if any participants took part in the survey across multiple years.

Conclusions

We found that despite the decreasing trend of drug use inside prisons in Iran, around one out of every four incarcerated people had recently used drugs inside prison. Current prison drug programs in Iran primarily target opioid use, neglecting the prevalent issue of stimulant use. This oversight may contribute to ongoing substance use despite available OAT services. To address this gap, it is essential to incorporate comprehensive interventions for stimulant use disorders into prison mental health services. Expanding treatment options would provide more holistic support for incarcerated individuals facing various substance use challenges.