Substance use disorders negatively affect global disease burden. Effective preventive interventions are available, but whether they provide value for money is unclear.

This review looks at the cost-effectiveness evidence of preventive interventions for cannabis use, opioid misuse and illicit drug use.

Literature search was undertaken in Medline, CINAHL, PsycINFO, EconLit through EBSCOhost and EMBASE, up to May 2021. Grey literature search was conducted as supplement. Studies included were full economic evaluations or return-on-investment (ROI) analyses for preventing opioid misuse, cannabis and illicit drug use. English-language restriction was used. Outcomes extracted were incremental cost-effectiveness ratios (ICER) or ROI ratios, with costs presented in 2019 United States dollars. Quality was assessed with the Drummond checklist.

Eleven full economic evaluation studies were identified from 5674 citations, with all studies conducted in high-income countries. Most aimed to prevent opioid misuse (n = 4), cannabis (n = 3) or illicit drug use (n = 5). Modelling was the predominant methodology (n = 7). Five evaluated school-based universal interventions targeting children and adolescents (aged <18 years). Five cost–benefit studies reported cost-savings. One cost-effectiveness and two cost–utility analysis studies supported the cost-effectiveness of interventions, as ICERs fell under prespecified value-for-money thresholds.

There are limited economic evaluations of preventive interventions for opioid misuse, cannabis and illicit drug use. Family-based intervention (ParentCorps), school-based interventions (Social and Emotional Training and Project ALERT) and a doctor's programme to assess patient risk of misusing narcotics (‘the Network System to Prevent Doctor-Shopping for Narcotics’) show promising cost-effectiveness and warrant consideration.

Drug classes are grouped based on their chemical and pharmacological properties, but prescription and illicit drugs differ in other important ways. Potential differences in genetic and environmental influences on the (mis)use of prescription and illicit drugs that are subsumed under the same class should be examined. Opioid and stimulant classes contain prescription and illicit forms differentially associated with salient risk factors (common route of administration, legality), making them useful comparators for addressing this etiological issue.

A total of 2410 individual Australian twins [Mage = 31.77 (s.d. = 2.48); 67% women] were interviewed about prescription misuse and illicit use of opioids and stimulants. Univariate and bivariate biometric models partitioned variances and covariances into additive genetic, shared environmental, and unique environmental influences across drug types.

Variation in the propensity to misuse prescription opioids was attributable to genes (41%) and unique environment (59%). Illicit opioid use was attributable to shared (71%) and unique (29%) environment. Prescription stimulant misuse was attributable to genes (79%) and unique environment (21%). Illicit stimulant use was attributable to genes (48%), shared environment (29%), and unique environment (23%). There was evidence for genetic influence common to both stimulant types, but limited evidence for genetic influence common to both opioid types. Bivariate correlations suggested that prescription opioid use may be more genetically similar to prescription stimulant use than to illicit opioid use.

Prescription opioid misuse may share little genetic influence with illicit opioid use. Future research may consider avoiding unitary drug classifications, particularly when examining genetic influences.

To describe the prevalence of low serum Se and determine whether HIV, hepatitis C virus (HCV) and/or the types of drugs used are associated with serum Se in a cohort of infected and uninfected drug users.

Independent correlates of low serum Se levels based on data collected from food recalls, physical examinations and clinical questionnaires were identified using multivariate regression analysis.

Buenos Aires, Argentina

A total of 205 (twenty-five female and 180 male) former and current drug users.

Drug users had an average serum Se level of 69·8 (sd 32·8) μg/dl, and 82 % were considered deficient (<85 μg/dl). Multivariate analyses found that HIV- and/or HCV-infected individuals had lower mean Se compared with healthy, uninfected drug users (HIV/HCV co-infection: −25·3 μg/l (se 7·6), P = 0·001; HIV alone: −28·9 μg/l (se 6·9), P < 0·001; HCV alone: −19·4 μg/l (se 7·1), P = 0·006). Current and previous drug use was associated with higher serum Se. Cigarette smoking and heavy alcohol consumption were not found to be associated with Se status.

Low serum Se levels are highly prevalent among drug users in Buenos Aires, Argentina. Se supplementation and/or dietary interventions may be warranted in drug users who are at high risk for HIV and/or HCV infection.

Clinically ascertained reports suggest that boys and girls with attention deficit hyperactivity disorder (ADHD) may differ from each other in their vulnerability to substance use problems.

A total of 1545 Finnish adolescents were assessed for DSM-IV-based ADHD symptoms by their parents and classroom teachers using standardized rating scales at age 11–12 years. At age 14, substance use disorders and psychiatric co-morbidity were assessed with the Semi-Structured Assessment for the Genetics of Alcoholism, providing DSM-III-R/DSM-IV diagnoses for Axis I disorders. At age 17.5, substance use was assessed by multi-item questionnaire.

Although baseline ADHD symptoms were less common among females, they were more predictive of adverse substance use outcomes once conduct disorder and previous substance use were controlled for. Only in females were baseline ADHD symptoms significant predictors of alcohol abuse and dependence and illicit drug use at age 14. At the age of 17.5, parents' reports of inattentiveness and hyperactivity were significant predictors for frequent alcohol use in both sexes, but they were more predictive of frequent alcohol and illicit drug use in girls. Impulsivity in teachers' ratings predicted frequent alcohol use and illicit drug use in boys. Parental reports of inattentiveness in their 11-/12-year-old daughters were a consistent predictor for illicit drug use across adolescence.

Inattentiveness and hyperactivity may be more predictive of alcohol use disorders and maladaptive patterns of alcohol and illicit drug use among girls than boys. The importance of these behavioural symptoms should be assessed further in the community, as they could jeopardize adolescents' successful transitioning into adult roles.