The changing patterns and correlates of population‐level polysubstance use in Australian youth: a multi‐group latent class analysis of nationally representative samples spanning 12 years

Abstract

Aims To (1) identify population‐level classes of polysubstance use among young Australians between 2004 and 2016, (2) test if these classes changed over the same period, in terms of class prevalence and probabilities of substance use within each class, and (3) identify demographic and health‐related correlates of polysubstance use. Design Repeated cross‐sectional nationally representative household surveys. Setting All Australian states/territories. Participants Young adult samples (aged 18–30 years; 58% females) from the National Drug Strategy Household Surveys (n = 20 350) Measurements Outcomes were the extent of past‐year use of 10 licit (e.g. alcohol), and illicit substances (e.g. cannabis) were used to derive polysubstance use classes. The correlates were gender, age, psychological distress, general health, language background, personal income, education level, remoteness of residence and socio‐economic index for area of residence. Findings Three polysubstance use classes were consistently identified between 2004 and 2016 (SSABIC: 188349): minimal users (MU, ~60%), mainly tobacco, alcohol and cannabis users (TAC, ~30%) and extended range polysubstance users (POLY, ~10%). There were substantial changes in use of different substances within each class over the study period. For example, smoking decreased in all classes (P < 0.05), while harmful alcohol use only decreased in the first two classes (P < 0.05). Factors associated with TAC and POLY were similar over the study period. These included: being male and having an English‐speaking background, a high level of psychological distress, suboptimal health and high personal income. Living in an affluent area was associated with reduced likelihood of being TAC, but an increased likelihood of being POLY. Conclusion At the population‐level among young Australians between 2004 and 2016, six in 10 did not engage in polysubstance use; four in 10 used a limited range of substances (mainly alcohol, tobacco and cannabis) and one in 10 used an extended range of substances. Over time, the types of substance within the extended polysubstance use class changed substantially.

Clinical symptoms and personality traits predict subpopulations of treatment-seeking substance users

“…Research has most commonly reported of a large group of individuals with a high probability of alcohol or cocaine use disorder (Hedden et al, 2010;Schwartz et al, 2010), and this group represents the vast majority of treatment seekers in the Spanish context (EMCDDA, 2019). The presence of classes characterized by cocaine as primary substance, cannabis as secondary, and additional alcohol/other drugs use (class 4) and by alcohol as primary and cannabis as secondary substance (class 5) is also in line with previous studies (Bailey et al, 2019;Chan et al, 2020;Hedden et al, 2010;Timko et al, 2017). Last, individuals with heroin as primary substance, cocaine as secondary and additional alcohol use (class 6) represent a subpopulation, which, considering the current low prevalence of heroin use in Spain (Plan Nacional Sobre Drogas, 2019), may be related to the so-called heroin epidemic that happened during the 1980s (Sánchez-Niubò et al, 2009), but may also be of interest to other countries in light of the upward trend of heroin use and overdose in the United States and Europe (NIDA, 2018b).…”

“…Against this background, there is a growing interest in exploring subpopulations of substance users using a person-centered approach, such as latent class analysis, which identifies similar patterns of substance use without a priori classification based on the use of specific drugs (Bailey et al, 2019;Chan et al, 2020;Garey et al, 2020;Gjersing & Bretteville-Jensen, 2018;Martínez-Loredo et al, 2019;Salom et al, 2016;Schwartz et al, 2010). However, this approach is still underused in community treatment-seeking adults with SUDs, which may hamper clinically relevant results in terms of treatment success.…”

Commentary on Chan et al. (2020): Solving the puzzle of why substance use is declining among young people requires a multi‐substance perspective

“…The findings of Chan et al [6] are consistent with previous research indicating that polysubstance use is common, substance use clusters and trends in different substances are related. Therefore, a shift away from the singlesubstance approach-which still dominates research and policy-is warranted if we are to understand and successfully address substance-related harms.…”

“…Remarkable declines in smoking and drinking have been recorded among secondary school students in most high‐income countries globally, with cannabis use also declining in many countries since a peak in the late 1990s or early 2000s . Chan et al demonstrate that, at least in Australia, this behavioural shift is not limited to secondary school students, and has also occurred in young adults aged 18‐30 years.…”

Polysubstance use in young people accessing residential and day‐treatment services for substance use: substance use profiles, psychiatric comorbidity and treatment completion

“…Epidemiological studies utilizing LCA have also found three class solutions that include wide-ranging substance users (including polysubstance use involving legal and illegal substances), amphetamine-only users and a class characterized by more commonly used substances (e.g. alcohol, tobacco and cannabis use[10,37]). The second aim examined the association between substance use class, mental health symptoms, QoL and service type.…”