Exploring Polydrug Use Among Individuals with Heroin Dependence: A Longitudinal Study on Cannabis Products


Polydrug use, the concurrent use of multiple substances, is prevalent among individuals with opioid use disorders (OUD) and has been associated with worsened health outcomes (Compton et al., 2021). Cannabis, in particular, is frequently used by those with OUD, with one to two-thirds reporting regular consumption (Kral et al., 2015; Rosic et al., 2021).

This trend may be fueled by the growing interest in cannabis as a potential substitute or complement to opioids for pain management or withdrawal symptom relief (Humphreys & Saitz, 2019; Wiese & Wilson-Poe, 2018). Understanding the types of cannabis consumed by individuals with OUD and the potential harm they may be exposed to is crucial, given the elevated risk of adverse health outcomes in this population (Degenhardt et al., 2018).

Variation in Cannabis Products

Cannabis comprises over 140 different cannabinoids, with delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) being the most prevalent (Hanuš et al., 2016). THC is responsible for the psychoactive effects, or ‘high,’ associated with cannabis use (Bhattacharyya et al., 2010). CBD, on the other hand, is a non-psychoactive cannabinoid with potential therapeutic applications (Campos et al., 2012; McPartland et al., 2015). The concentrations of THC and CBD in cannabis products vary based on factors such as plant genetics, growing conditions, and preparation methods.

Unpollinated female plants (sinsemilla) can yield higher THC concentrations, while fertilized seeded plants (bush/outdoor grown) are generally less potent but may have similar CBD content. Cannabis concentrates, produced through extraction methods like butane or super-critical carbon dioxide, boast extremely high THC concentrations and negligible CBD levels (Raber et al., 2015). Despite this variability, there is a global trend toward the use of high-potency cannabis products (Freeman et al., 2021).

Effects of THC and CBD

THC acts as a partial agonist at cannabinoid type 1 receptors, leading to psychoactive effects (Bhattacharyya et al., 2010). Clinical trials have demonstrated dose-dependent effects of THC on intoxication, cognitive impairment, anxiety, and psychotic-like symptoms (Curran et al., 2002; D’Souza et al., 2004). Higher THC products have been associated with an increased risk of cannabis use disorder (CUD), psychotic conditions, anxiety, and depression (Craft et al., 2019; Freeman & Winstock, 2015; Di Forti et al., 2019; Mackie et al., 2021; Chan et al., 2017; Morgan et al., 2012).

CBD, with its low affinity for cannabinoid receptors, is being explored as an alternative therapy for conditions such as psychosis and epilepsy (Bonaccorso et al., 2019). Clinical trials have suggested its potential efficacy in treating heroin use disorder and CUD (Hurd et al., 2019; Freeman et al., 2020).

When consumed alongside THC, CBD may mitigate some of the negative effects, as observed in naturalistic studies where higher CBD content was associated with reduced cognitive impairments, psychotic-like experiences, and anxiety disorders (Demirakca et al., 2011; Morgan & Curran, 2008; Morgan et al., 2010a, 2010b). However, the protective effects of CBD against acute THC harms are still under investigation (A. Englund et al., 2013; A. Englund et al., 2022).

Polydrug Use and Cannabis Products

Despite high rates of co-occurring cannabis use among those with other substance use disorders (Hasin & Walsh, 2020), there is a paucity of research on the prevalence and impact of various cannabis products on individuals with OUD. Notably, a UK longitudinal birth cohort found associations between high-potency cannabis use and increased likelihood of using other drugs and developing tobacco dependence (Hines et al., 2020).

Current Study Objectives

The present study seeks to address these gaps by investigating the prevalence, frequency, and quantity of past 12-month use of various cannabis products among a naturalistic longitudinal cohort of individuals with heroin dependence. Three main objectives will guide the study: (a) assessing the prevalence and patterns of cannabis product use, (b) examining the relationship between baseline characteristics and cannabis product use, and (c) exploring the associations between cannabis product use and outcomes over an 18–20 year period.


The present study is among the first to comprehensively explore the prevalence and long-term associations of various cannabis products among individuals with heroin dependence. The findings reveal a high prevalence of cannabis use within this cohort, with 99.0% of participants having ever used cannabis and 52.1% reporting use in the past 12 months. Notably, high-potency/indoor-grown cannabis emerged as the most commonly used type since the first use and over the past 12 months, with fewer participants opting for low potency/outdoor grown or other types of cannabis.

Prevalence of High-Potency Cannabis Use

The prevalence of high-potency/indoor-grown cannabis within this cohort aligns with broader trends observed in illicit drug monitoring systems. Recent data from Australia showed that 91% of individuals reporting recent cannabis use were consuming indoor-grown, reflecting similar patterns seen in Europe, North America, and Australia over the past decade (Sutherland et al., 2021; World Drug Report, 2021; Freeman et al., 2021). The shift towards high-potency products may contribute to the overall increase in THC concentrations within herbal cannabis globally.

Associations with Age and Other Covariates

The study’s univariable regression analysis identified several baseline measures associated with the common use of high-potency cannabis in the past 12 months, including age, past month cannabis use, and past month daily cannabis use. Furthermore, certain 18–20-year covariates, such as owning or renting accommodation, incarceration since the last interview, past month amphetamine use, and a PTSD diagnosis, exhibited some evidence of association. However, a multivariable model revealed that age at baseline was the sole significant factor associated with the common use of high-potency cannabis.

The association between age and high-potency cannabis use is consistent with prior evidence, suggesting that young people are at greater risk of developing cannabis dependence when using high-potency products (Freeman & Winstock, 2015). Intervention programs targeting young individuals to reduce the use of potent cannabis products could potentially mitigate associated harms.

Cannabis Use Patterns and Health Outcomes

Interestingly, the study found that while just as many participants were using low potency/outdoor grown less than monthly, over 80% of those using cannabis daily reported the use of high potency/indoor-grown cannabis. This aligns with previous findings indicating that THC exhibits dose-related effects on drug reinforcement and that THC levels in cannabis markets are positively associated with first-time cannabis admissions to treatment centers.

Contrary to some prior research, this study did not find evidence of an association between high-potency cannabis use and poorer cognitive performance, the use of other drugs, or major depression. These discrepancies may arise from differences in study populations or a potential ceiling effect, as individuals with OUD may already be experiencing high levels of adverse health outcomes. Additionally, limited statistical power may have impacted the detection of differences in certain health outcomes based on cannabis type.

Limitations and Future Directions

Several limitations must be considered when interpreting the findings. The study relied on self-reported measures of cannabis product use, providing only a proxy for exposure to THC and CBD. The inability to determine precise cannabinoid content may impact the accuracy of the findings. Furthermore, the study’s focus on high-potency/indoor-grown herbal cannabis may not fully capture the nuances associated with other cannabis products.

Despite these limitations, this pioneering study sheds light on the prevalence and potential associations of various cannabis products among individuals with heroin dependence. The high prevalence of cannabis use within this population emphasizes the need for continued research to monitor the long-term effects of different cannabis products. Understanding the complex interplay between polydrug use and the choice of cannabis products is crucial for developing targeted interventions and support strategies tailored to the unique needs of individuals with opioid use disorders.

reference link : https://link.springer.com/article/10.1007/s11469-023-01071-5


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