Introduction
Substance use is a significant cause of disability and premature mortality globally [
1‐
3]. It puts a huge burden on societies and governments significantly, including high economic costs, healthcare expenditures, lost productivity, increased violence, and poor treatment compliance [
4]. The World Health Organization (WHO) estimates that in 2021, approximately 296 million people aged 15–64 engaged in substance use, reflecting a 26% increase over the preceding decade [
5]. Cannabis constituted the predominant choice, with 219 million users, followed by opioids (60 million users) and methamphetamine (32 million users) worldwide [
5]. However, the prevalence of substance use and the associated disease burden differed significantly across countries and varied among geographical regions [
6]. According to the Global Burden of Disease report, the most substantial contributors to disability-adjusted life-years (DALYs) attributable to substance use were identified in the domains of substance use disorders (20.4 million DALYs), cancer (1.6 million DALYs), liver cirrhosis (4.8 million DALYs), and human immunodeficiency virus (HIV) (3.2 million DALYs) [
6]. Moreover, substance use is responsible for almost 452,000 deaths annually.
Opioid dependence is one of the most common substance use disorders, with rates of 1.2% of the adult population worldwide, half of which is situated in South Asia or South-West Asia [
5]. Moreover, opioids persist as the most lethal category of substances, responsible for approximately two-thirds of direct substance-related deaths, primarily through overdoses [
5]. Consistently with global trends, substance use, particularly opium in Iran, has increased recently [
7]. This is due to several factors, including the fact that Iran shares its border with Afghanistan, the world’s largest producer of opium, and Iran is a significant route for opium transport to Europe [
8]. Another significant factor is Iran’s primary host of Afghan refugees (over three million). Given the historical prevalence of opium use among the Afghan population, prior evidence depicted the continuation of opium use among Afghan refugees in Iran [
9]. These factors contribute to the escalated prevalence of opium use in Iran, facilitated by easy accessibility and low cost. In line with this, the WHO report illustrated Iran has the highest rate of opium users worldwide, and opium use disorder among Iranians is three times higher than global usage [
10]. Moreover, previous literature demonstrated that around two million people in Iran are estimated to consume illicit substances, which equals 2.7% of the total population [
11].
In accordance with robust evidence, substance use was strongly associated with mental, physical, and social health problems [
12‐
14]. In spite of the high spectrum of problems associated with industrial substances, opium use as a traditional substance is related to several physical disabilities, including cancers and cardiovascular diseases [
7].. Nevertheless, with the introduction of various health policies, substance use has still significantly increased in recent years [
15‐
18]. In addressing this issue, health policymakers should be aware of the determinants influencing substance use to develop and implement proper prevention programs, potentially leading to a reduction in the incidence of substance use in society [
19].
As of yet, a number of epidemiological and regional surveys have assessed substance use prevalence among Iranians, but their results were curtailed by small sample sizes and demographic differences among study populations [
20,
21]. Furthermore, the prevalence of substance and opium use remains uncertain in Tehran, the capital of Iran, and available data are sparse and only encompass limited areas of the city. Additionally, previous investigations suggest that the male gender, younger age, socioeconomic status, as well as alcohol and tobacco use [
22,
23]. Nevertheless, comprehensive data on predictors or determinants of substance and opium use in Tehran is still lacking.
Considering the ongoing population changes in Tehran, conducting a comprehensive study on substance use prevalence would be necessary to provide suitable insight into the current situation of substance use in Tehran for developing healthcare-related programs and governmental implementations [
24,
25]. Therefore, as the first comprehensive investigation, we aimed to evaluate the prevalence and epidemiology of substance use, notably opium, in Tehran utilizing the recruitment phase data from the Tehran Cohort study (TeCS) data with a focus on identifying independent determinants associated with opium use.
Discussion
The current study aimed to determine the prevalence, patterns, and risk factors associated with substance use among adults 35 years old and greater in the Tehran population. As the first comprehensive investigation, our findings revealed a prevalence of 5.6% for substance use among the study population, with opioids being the most commonly used substance among our population. In addition, our results illustrated that opium use was independently associated with male gender, lower education levels, and alcohol and tobacco consumption.
Across the globe, substance use significantly contributes to major health-related problems, such as an escalation in infectious diseases such as hepatitis C and HIV, as well as an increase in physical and psychological disabilities [
32‐
34]. Communities and governments are also confronted with significant challenges due to substance addiction, including the burden of substantial costs, high healthcare costs, functional impairment, violence, and criminal activities. According to the World Drug Report, a concerning rise in substance use has occurred over the past decade [
35]. The report states that from 2006 to 2015, the percentage of substance users worldwide increased from 4.9 to 5.6%. This upward trend has considerably impacted the lives of millions worldwide, affecting approximately 275 million individuals.
There exists a long-term historical practice of employing opium as a traditional therapy in regions where opium is traditionally produced [
36]. In Afghanistan, women engaged in the carpet weaving industry resort to opium for pain relief and to relax their children. Moreover, in Morocco, the opium poppy has been traditionally utilized to relieve pain, diarrhea, cough, and insomnia. Additionally, opium has conventionally been utilized as a pain-relieving substance, particularly among the elderly population in Iran [
36]. A survey conducted in 2010 demonstrated that substance use in Iran is linked to tripled mortality rates among females and almost doubled mortality rates among males from 1990 to 2010 [
33,
37].. In addition, based on a 2005 rapid assessment of substance use among the Iranian population, 1 200 000–1 800 000 people (2.4 − 2.65%) had a history of substance use [
38]. Moreover, the National Survey on Substance Users and the National Survey on Mental Health estimated that substance use was 2.65% and 2.8%, respectively [
39,
40]. Besides, the Iranian household mental health survey conducted in 2011 demonstrated that the prevalence of substance use is 2.09% and 2.44% based on DSM-IV and DSM-5, respectively [
17]. Concerning related studies [
11,
18,
41], our finding highlights the increasing trend of substance use in the Tehran population.
In accordance with global trends, males were more likely to use substances than females [
18,
39,
42]. Moreover, the incidence of substance use exhibited a consistent upward trend in individuals aged 35 and above, reaching its apex within the 55–64 age group. This finding is alarming since the elderly population is more vulnerable to the adverse effects of substance use due to age-related physiological changes. Additionally, the association between lower educational level [
18,
39], alcohol and tobacco consumption [
42,
43], lower physical activity [
43], and lesser BMI [
43,
44] and substance use has been revealed in several studies. Prior investigations have also explained that the prevalence of substance use in Iran peaks at older ages compared to international reports [
45,
46]. Albeit, there is a controversy over the results. Some studies support our findings by depicting a higher prevalence of substance use in the 5th and 6th decades of life [
18,
39]; on the other hand, other studies considered the 3rd and 4th decades of life the highest prevalence of substance use [
17]. Also, the prevalence of substance use has been reported in prior studies to be higher in previously married (divorced, separated, or widowed) individuals [
18,
39]; However, our findings demonstrated no association between marital status and substance use [
18].
In addition, it should be mentioned due to ongoing population changes and different ethnicities and populations within Iran, substance use, particularly opioid use, is prevalent at varying rates among regions. Regarding prior studies, the northern and southern parts of Iran have been found to have a higher prevalence of substance use [
43,
47]. Evidence has also illustrated a higher prevalence of opioid use in Iran’s rural population than in its urban residents [
48,
49]. As a novel finding of our study Tehran district substance users’ concertation in suburban areas, especially southern parts was significantly higher than in other areas. Additionally, we used separate analyses for each gender because the disparity in the prevalence of substance use between the sexes is evident in Middle Eastern populations. Since opium use and smoking are considered taboo in women, Middle Eastern women demonstrate considerably lower rates of substance use in comparison to their counterparts in Western regions [
50]. Further, it is imperative to mention that the available data on substance use among women in Iran, particularly in Tehran, was limited, which also underscored the significance of our findings.
Conversely, to recent literature [
51], our study also indicates that drug use is more prevalent among employed participants, mainly men. Concerning this observation, we can gain insight into the relationship between substance use and employment status. Various factors could contribute to this phenomenon, including stress and pressure associated with work demands [
52]. In addition, substance use patterns may be influenced by the work environment itself. Further, the availability and social dynamics within the workplace can contribute to the greater prevalence of substance use among employed individuals, particularly men.
These results highlight that substance use, particularly opium, is a major public health challenge in the region that requires tailored interventions to mitigate its harms and disabilities. Moreover, regular surveillance of substance use trends and risk factors is essential for developing evidence-based policies and programs. Ultimately, a collaborative effort from policymakers, healthcare providers, and the community is needed to address the issue of substance use and its consequences in Iran and other affected countries.
Strengths and limitations
The primary strength of this study lies in our provision of the first investigation and comprehensive data on substance and opium use in Tehran. The findings have the potential to serve as a foundational cornerstone for future studies and the development of public health plans and interventions in order to curb substance use, particularly opium, irregularly in Tehran. Similar to all cross-sectional studies, the current study also has some limitations, such as the presence of non-responders poses a challenge to accurately reporting the prevalence of substance and opium use in Tehran. Moreover, the observational design may be confounded by unknown variables. Furthermore, the limited number of females with substances in some analyses might impede the identification of significant differences. The broad objectives of TeCS necessitated the inclusion of only general inquiries about substance use status due to time constraints during data collection. Participants were interviewed for multiple questionnaires, and anthropometric measurements were conducted in a limited half-day session. Subsequently, detailed data on substance behaviors, such as the age of initiation and the exact amount of consumption, was lacking. Additionally, it is important to note that TeCS excluded adults aged ≥ 35 years,, potentially impacting our estimations, particularly for emerging substances like cannabis, which are believed to be more prevalent among the younger population.
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