Polysubstance Use: When Multiple Addictions Overlap

Introduction

Polysubstance use — the simultaneous or sequential use of multiple substances — is the norm rather than the exception in addiction. Research consistently shows that the majority of people with substance use disorders use more than one substance. Understanding polysubstance use is essential for accurate assessment, appropriate treatment planning, and safe management of withdrawal and pharmacotherapy.

Key Definitions

Polysubstance use: The use of two or more substances, either simultaneously or in close temporal proximity.

Polysubstance use disorder: A DSM-5 diagnosis for people who meet criteria for substance use disorder for multiple substances.

Synergistic effects: Drug interactions in which the combined effect is greater than the sum of the individual effects. Common with CNS depressants.

Cross-tolerance: Tolerance to one substance that reduces the effect of another substance in the same class. For example, tolerance to alcohol reduces the effect of benzodiazepines.

Sequential use: Using different substances at different times — for example, using stimulants during the day and CNS depressants at night to manage the effects of each.

Prevalence and Patterns

Research on polysubstance use reveals several important patterns:

Prevalence: Studies consistently find that 50-80% of people seeking treatment for substance use disorders use multiple substances. Among people with alcohol use disorder, approximately 50% also use cannabis, and 20-30% use opioids or stimulants. Among people with opioid use disorder, alcohol and benzodiazepine use are extremely common.

Common combinations:

• Alcohol + benzodiazepines: Both enhance GABA function; combined use dramatically increases CNS depression and overdose risk.
• Opioids + benzodiazepines: The most dangerous combination — responsible for a significant proportion of opioid overdose deaths. Both suppress breathing; combined use dramatically increases respiratory depression.
• Alcohol + opioids: Similar to opioids + benzodiazepines — combined CNS depression increases overdose risk.
• Stimulants + opioids (speedball): The stimulant masks the sedating effects of the opioid, allowing higher opioid doses. When the stimulant wears off, the opioid effect is unmasked, increasing overdose risk.
• Alcohol + stimulants: Stimulants mask the sedating effects of alcohol, allowing higher alcohol consumption. Cocaethylene — a compound formed when cocaine and alcohol are used together — is more toxic to the heart than either substance alone.
• Cannabis + other substances: Cannabis is commonly used alongside virtually every other substance. It may modulate the effects of other substances through the endocannabinoid system.

Why Polysubstance Use Is Common

Several factors contribute to the prevalence of polysubstance use:

Self-medication: People may use multiple substances to manage different symptoms — stimulants for energy and focus, CNS depressants for anxiety and sleep, opioids for pain.

Managing withdrawal: People may use one substance to manage the withdrawal effects of another — for example, using alcohol to manage opioid withdrawal, or using benzodiazepines to manage alcohol withdrawal.

Enhancing effects: Some combinations are used deliberately to enhance the effects of one or both substances — for example, combining alcohol with cocaine to enhance euphoria.

Shared vulnerability: The same genetic and neurobiological factors that increase vulnerability to one substance use disorder also increase vulnerability to others. People with addiction are generally more vulnerable to addiction to multiple substances.

Availability: In the current drug supply, polysubstance exposure is often inadvertent — fentanyl contamination of cocaine and other drugs means that people who intend to use only one substance may be exposed to multiple substances.

Health Risks of Polysubstance Use

Overdose risk: Polysubstance use dramatically increases overdose risk, particularly with combinations of CNS depressants. The combination of opioids and benzodiazepines is responsible for approximately 30% of opioid overdose deaths. The combination of alcohol and opioids is similarly dangerous.

Cardiovascular risk: Some combinations — particularly stimulants with alcohol (producing cocaethylene) or stimulants with opioids — increase cardiovascular risk beyond that of either substance alone.

Psychiatric risk: Polysubstance use is associated with higher rates of psychiatric comorbidity, more severe psychiatric symptoms, and worse treatment outcomes than single-substance use disorders.

Treatment complexity: Polysubstance use complicates treatment — withdrawal management must address multiple substances, pharmacotherapy interactions must be considered, and behavioral treatment must address multiple use patterns.

Treatment Challenges and Approaches

Comprehensive assessment: Accurate assessment of all substances used — including alcohol, cannabis, and prescription medications that may not be spontaneously reported — is essential for treatment planning. Urine drug testing and structured assessment tools can help identify the full scope of substance use.

Withdrawal management: Withdrawal from multiple substances must be managed simultaneously. The most medically dangerous withdrawals — alcohol and benzodiazepines — must be prioritized. Opioid withdrawal can be managed with buprenorphine or methadone.

Pharmacotherapy interactions: Medications used in addiction treatment can interact with substances of misuse. For example, methadone can prolong the QT interval, and this risk is increased by other substances that affect cardiac conduction. Buprenorphine can precipitate withdrawal if given to someone with recent opioid use.

Integrated behavioral treatment: Behavioral treatment for polysubstance use should address all substances used, not just the primary substance. Integrated treatment that addresses multiple substances simultaneously is more effective than sequential treatment of individual substances.

Harm reduction: For people who are not ready to stop all substance use, harm reduction approaches — reducing the most dangerous use patterns, providing naloxone, testing for fentanyl — can reduce harm while maintaining engagement.

Frequently Asked Questions

Is polysubstance use harder to treat than single-substance use?
Generally yes. Polysubstance use is associated with more severe addiction, more complex withdrawal, more psychiatric comorbidity, and worse treatment outcomes than single-substance use. However, effective treatment is available, and many people with polysubstance use disorders achieve long-term recovery.

Should I tell my treatment provider about all the substances I use?
Yes, absolutely. Accurate disclosure of all substances used is essential for safe and effective treatment. Withholding information about substance use can lead to dangerous drug interactions, inadequate withdrawal management, and ineffective treatment. Treatment providers are not there to judge — they need complete information to provide safe care.

Can I be treated for multiple substance use disorders simultaneously?
Yes. Integrated treatment that addresses multiple substance use disorders simultaneously is generally more effective than sequential treatment. Many treatment programs are equipped to address polysubstance use.

Key Takeaways

• Polysubstance use is the norm in addiction — the majority of people with substance use disorders use multiple substances.
• Certain combinations — particularly opioids + benzodiazepines and opioids + alcohol — dramatically increase overdose risk.
• Polysubstance use complicates treatment through complex withdrawal management, pharmacotherapy interactions, and multiple behavioral targets.
• Comprehensive assessment of all substances used is essential for safe and effective treatment.
• Integrated treatment addressing all substances simultaneously is more effective than sequential treatment.

Additional Resources

Related articles on Sobriety Navigator: Alcohol Use Disorder, Opioid Use Disorder, Benzodiazepine Dependence, Medication-Assisted Treatment.