Recent research indicates that adolescents (12-17) who misuse more than one substance – or engage in polysubstance use – may be at higher risk to develop substance use disorders in adulthood. Some evidence also suggests that this same age group may be more likely to move from polysubstance misuse of cigarettes and marijuana to polysubstance misuse of non-medical use of prescription drugs (e.g., opioids or benzodiazepines) with illicit drugs (e.g., cocaine or methamphetamine) as adults.

Polysubstance Misuse

Individuals engaged in polysubstance misuse typically misuse two or more substances at the same time or alternate between two or more substances. The prevalence of polysubstance use is likely underestimated or understudied because the current Diagnostic and Statistical Manual of Mental Disorders (DSM) eliminated the category.

Nonetheless, individuals do in fact misuse more than one substance at a time, for a variety for reasons, with problematic outcomes.

Early research suggests at least three possible reasons for this behavior:

• Seeking to multiply or enhance the effects of the drugs, that is, to intensify the euphoric effect sought by the user
• Seeking to ameliorate the withdrawal symptoms from one of the drugs misused
• Peer pressure or subculture influence to simultaneously use more than one substance

Employing innovative statistical methods, researchers seeking for more specific common features among polysubstance misusers typically create different subgroups of polysubstance use. The idea here is to get a clearer picture of the most commonly combined substances in polysubstance use along with other characteristics of individuals that combine any given group of drugs.

Polysubstance Use: Categories

While there are many different ways of dividing up these subgroups, one simple model classifies them this way:

• Non-use
• Limited range (alcohol, tobacco, and marijuana)
• Moderate range (amphetamines included to the above class)
• Extended range (non-medical use of prescription drugs and other illicit drugs).

Further research into these classes through new data collection may help public health scientists hone on more common features defining limited, moderate, or extended range polysubstance users. For example, it may be the case that certain classes co-occur with certain mental health disorders and demographic features (rural vs. urban, employed vs. unemployed, or education level). When clinicians develops a finer grain picture of the characteristics of individuals in each of the polysubstance classes, they can then develop more efficient screening and assessment practices.

Consequences of Polysubstance Use

The presence of polysubstance use in any population, including adolescents and young adults, likely indicates poorer health outcomes in adulthood. Researchers looking at the above classes of polysubstance use were able to predict greater likelihood of a variety of impairments beyond substance use disorder.

Researchers in this study identified the following trends among different polysubstance users:

• Individuals who use alcohol and illicit drugs were more likely to have generalized anxiety disorder (GAD) and major depressive disorder (MDD)
• Individuals who use cannabis and other illicit drugs or non-medical prescription drugs are more likely to have higher rates of anxiety and/or more positive psychotic symptoms.

In addition to these specific observations, researchers noted that polysubstance use in adolescents may make them more vulnerable to neurotoxicity. Polysubstance use can cause damage to the nervous system in a variety of ways because of how the various substance interact. Initial research indicates polysubstance use can damage working memory.

More research into polysubstance use is necessary, especially given the connection between polysubstance use among adolescents and higher rates of substance use disorder among polysubstance users in adults. So far, the research suggests patterns, i.e. specific combinations or pairs of drugs misused. The better we understand the likelihood of those combinations or pairings, the better clinicians can screen and intervene effectively among individuals who are in treatment.