Steppingstone and gateway ideas: a discussion of origins, research challenges, and promising lines of research for the future

High Prevalence and Early Onsets: Legal and Illegal Substance Use in an Urban Cohort of Young Adults in Switzerland

INTRODUCTION

Debates about the legalization of illegal substances (e.g., cannabis) continue around the globe. A key consideration in these debates is the adequate protection of young people, which could be informed by current prevalence and age-of-onset patterns. For Switzerland, such information is limited, which is particularly true for women, despite advanced political efforts to legalize cannabis. The objective of the current study was to investigate substance use prevalence rates and ages of onset in a community-representative sample of female and male young adults in Switzerland.

METHODS

Data came from the Zurich Project on the Social Development from Childhood to Adulthood (z-proso). In 2018, participants (N = 1,180, 50.8% females) were ∼20 years old. Lifetime and past-year use of alcohol, tobacco, cannabinoids, stimulants, hallucinogens, opioids, and benzodiazepines were assessed with an extensive substance use questionnaire. Additionally, ages of onsets of the respective substances were estimated by averaging participants' self-reported ages of onsets from ages 13 to 20 (max. 4 assessments).

RESULTS

57% of 20-year-olds had used cannabinoids, 16% stimulants, 15% opioids (mostly codeine), and 8% hallucinogens in the past year. Males had higher prevalence than females for most drugs; nevertheless, females' prevalence rates were notably high. Legal substance use was typically initiated 1.3-2.7 years before legal selling age. Thus, almost half of the sample had consumed alcohol and tobacco by age 14. More than 40% of the total sample had smoked cannabis by age 16. Males initiated use of legal substances and cannabis earlier than females.

DISCUSSION

Our recent community-representative data suggested unexpectedly high levels and early onsets of substance use compared to a previous Swiss surveys and also the European average. Drug policy debates should consider urban substance use patterns when considering legalization efforts.

Persistence of extra-medical prescription pain reliever use and alcohol involvement among United States 12-20 year olds

The peak risk of first extramedical use of prescription pain relievers (PPRs) is in mid-adolescence, often after underage drinking has begun. This research aims to investigate discrete classes of similar young people based on their newly incident extramedical use of PPR and alcohol involvement, with empirical evaluation of the underlying structure of identified subgroups and their epidemiological distributions in the United States. The U.S. National Surveys on Drug Use and Health, 2002-2013, sampled, recruited, and assessed 24,789 newly incident extramedical PPR users ages 12-20 years, with self-interviews on PPR, alcohol, and covariates. Latent classes of persistence were formed using PPR and alcohol status variables. Then, age and sex were studied as potentially important predictors of class membership. Analysis-weighted estimates and delta method variances were derived. Three classes were distinguished by extramedical PPR and alcohol use patterns: (a) nonpersistent (79%), (b) intermittent (15%), and (c) persistent (6%). There were no differences across classes by age, but being female was associated with greater odds of being in the intermittent class or persistent class compared to the nonpersistent class. Presenting clinical features of alcohol and/or opioid dependence that have become manifest at or near time of first PPR use can be indicators of persisting in extramedical use of PPR, particularly for young people who have recently started extramedical PPR use. Persistent adolescent and young adult extramedical PPR users require tailored public health prevention and intervention strategies based on their vulnerability to continue use over time. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Does Starting to Smoke Cigars Trigger Onset of Cannabis Blunt Smoking?

Introduction

Among United States teens during the 1990s, increasing cigar use coincided with increasing use of tobacco cigar shells filled with cannabis, called "blunts." Cigar smokers are more likely to use cannabis, and we hypothesized that starting to smoke cigars might be a probabilistic "trigger" of blunt smoking. We turned to the case-crossover approach to evaluate this hypothesis.

Methods

Within US National Surveys on Drug Use and Health, 2009-2013, we identified a nationally representative sample of newly incident blunt smokers aged 12- to 21-years-old (n = 4868) and compared month-of-onsets for smoking of cigars and blunts. Using the subjects-as-their-own-controls case-crossover design, we specified the first month prior to blunt use as a "hazard interval" and the second month prior to blunt use as a "control interval." We used Mantel-Haenszel (MH) estimators to estimate the matched-pairs odds ratio (OR).

Results

The MH OR estimate was 1.7 (95% CI = 1.3, 2.3), with excess odds of cigar onsets during the hazard interval relative to the control interval. Two alternative control interval specifications yielded congruent estimates (OR = 2.7 and 2.9, respectively).

Conclusions

A short interval right after starting to smoke cigars may be one of increased risk of starting to smoke blunts. We discuss cigar, cigarillo, and "blunt wraps" control approaches that might reduce both tobacco and cannabis-related harms.

Implications

If this evidence is correct, increased market-targeting to promote youthful cigar and cigarillo smoking might be followed by increased rates of blunt smoking in a vulnerable population. As noted by others, enhanced risk of smoking-attributable harms might be a consequence of mixed tobacco-cannabis formulations.

Gene variants and educational attainment in cannabis use: mediating role of DNA methylation

Genetic and sociodemographic risk factors potentially associated with cannabis use (CU) were investigated in 40 cannabis users and 96 control subjects. DNA methylation analyses were also performed to explore the possibility of epigenetic changes related to CU. We conducted a candidate gene association study that included variants involved in the dopaminergic (ANKK1, NCAM1 genes) and endocannabinoid (CNR1, CNR2 gene) pathways. Sociodemographic data included gender, marital status, level of education, and body mass index. We used MeDIP-qPCR to test whether variations in DNA methylation might be associated with CU. We found a significant association between SNP rs1049353 of CNR1 gene (p = 0.01) and CU. Differences were also observed related to rs2501431 of CNR2 gene (p = 0.058). A higher education level appears to decrease the risk of CU. Interestingly, females were less likely to use cannabis than males. There was a significantly higher level of DNA methylation in cannabis users compared to controls in two of the genes tested: hypermethylation at exon 8 of DRD2 gene (p = 0.034) and at the CpG-rich region in the NCAM1 gene (p = 0.0004). Both genetic variants and educational attainment were also related to CU. The higher rate of DNA methylation, evidenced among cannabis users, may be either a marker of CU or a consequence of long-term exposure to cannabis. The identified genetic variants and the differentially methylated regions may represent biomarkers and/or potential targets for designs of pharmacological therapeutic agents. Our observations also suggest that educational programs may be useful strategies for CU prevention.

Nonmedical prescription opioids and pathways of drug involvement in the US: Generational differences

BACKGROUND

This study sought to specify (1) the position of nonmedical prescription opioids (NMPO) in drug initiation sequences among Millennials (1979-96), Generation X (1964-79), and Baby Boomers (1949-64) and (2) gender and racial/ethnic differences in sequences among Millennials.

METHODS

Data are from the 2013-2014 National Surveys on Drug Use and Health (n = 73,026). We identified statistically significant drug initiation sequences involving alcohol/cigarettes, marijuana, NMPO, cocaine, and heroin using a novel method distinguishing significant sequences from patterns expected only due to correlations induced by common liability among drugs.

RESULTS

Alcohol/cigarettes followed by marijuana was the most common sequence. NMPO or cocaine use after marijuana, and heroin use after NMPO or cocaine, differed by generation. Among successively younger generations, NMPO after marijuana and heroin after NMPO increased. Millennials were more likely to initiate NMPO than cocaine after marijuana; Generation X and Baby Boomers were less likely (odds ratios = 1.4;0.3;0.2). Millennials were more likely than Generation X and Baby Boomers to use heroin after NMPO (hazards ratios = 7.1;3.4;2.5). In each generation, heroin users were far more likely to start heroin after both NMPO and cocaine than either alone. Sequences were similar by gender. Fewer paths were significant among African-Americans.

CONCLUSIONS

NMPOs play a more prominent role in drug initiation sequences among Millennials than prior generations. Among Millennials, NMPO use is more likely than cocaine to follow marijuana use. In all generations, transition to heroin from NMPO significantly occurs only when both NMPO and cocaine have been used. Delineation of drug sequences suggests optimal points in development for prevention and treatment efforts.

Longitudinal Studies on the Etiology of Cannabis Use Disorder: A Review

PURPOSE OF REVIEW

This review summarizes the literature to date that has capitalized on the longitudinal research study framework in order to elucidate the etiology of cannabis use disorders (CUDs).

RECENT FINDINGS

The studies are mixed with respect to reliable predictors of CUD development. Of the studies outlined, the most consistently indicated risk factors for CUD development include: male sex, past cannabis and other substance use (especially tobacco), and the presence of pre/comorbid psychopathology (especially mood disorders). Social motives and peer involvement may also play a role in this transition. Many of these CUD risk factors appear to be distinct from other factors linked with overall cannabis use.

SUMMARY

CUD development is likely the product of interactions between biological, psychological, social, and environmental factors. However, many more well-planned and developmentally sensitive prospective studies are needed to identify specific and reliable risk factors for CUD development.

Obsolete tobacco control themes can be hazardous to public health: the need for updating views on absolute product risks and harm reduction

BACKGROUND

Leading themes have guided tobacco control efforts, and these themes have changed over the decades. When questions arose about health risks of tobacco, they focused on two key themes: 1) how bad is the problem (i.e., absolute risk) and 2) what can be done to reduce the risk without cessation (i.e., prospects for harm reduction). Using the United States since 1964 as an example, we outline the leading themes that have arisen in response to these two questions. Initially, there was the recognition that "cigarettes are hazardous to health" and an acceptance of safer alternative tobacco products (cigars, pipes, light/lower-tar cigarettes). In the 1980s there was the creation of the seminal theme that "Cigarettes are lethal when used as intended and kill more people than heroin, cocaine, alcohol, AIDS, fires, homicide, suicide, and automobile crashes combined." By around 2000, support for a less-dangerous light/lower tar cigarette was gone, and harm reduction claims were avoided for products like cigars and even for smokeless tobacco which were summarized as "unsafe" or "not a safe alternative to cigarettes."

DISCUSSION

The Surgeon General in 2014 concluded that by far the greatest danger to public health was from cigarettes and other combusted products. At the same time the evidence base for smokeless tobacco and alternative nicotine delivery systems (ANDS) had grown. Product innovation and tobacco/nicotine bio-behavioral, epidemiological and public health sciences demonstrate that low nitrosamine smokeless tobacco (e.g., Swedish snus), and ANDS have substantially lower harms than cigarettes. Going forward, it is important to sharpen themes and key messages of tobacco control, while continuing to emphasize the extreme lethality of the inhaled smoke from cigarettes or from use of any combusting tobacco product. Implications of updating the leading themes for regulation, policymaking and advocacy in tobacco control are proposed as an important next step. A new reframing can align action plans to more powerfully and rapidly achieve population-level benefit and minimize harm to eliminate in our lifetime the use of the most deadly combustible tobacco products and thus prevent the premature deaths of 1 billion people projected to occur worldwide by 2100.

Age of Sexual Debut and Cannabis Use in the United States

BACKGROUND

Understanding the interrelationships between risky health behaviors is critical for health promotion efforts. Conceptual frameworks for understanding substance misuse (e.g. stepping-stone models) have not yet widely incorporated other risky behaviors, including those related to sexual health.

OBJECTIVES

The goals of this study were to assess the relationship between early sexual debut and cannabis use, examine the role of licit substance use in this association, and evaluate differences by gender and race/ethnicity.

METHODS

Data came from the National Comorbidity Survey-Replication (NCS-R). Primary analysis was restricted to respondents who reported sexual debut at ≥12 years (n = 5,036). Age at sexual debut was categorized as early (<18 years), average (18 years) and late (>18 years). Logistic regression was used to assess the relationship between age at sexual debut and cannabis use. Interaction terms were used to evaluate effect modification by gender and race/ethnicity.

RESULTS

Later age of sexual debut was associated with lower odds of cannabis use relative to the average age of debut (AOR = 0.50, 95% CI = 0.37-0.66). For every year that respondents delayed their sexual debut, the relative odds of lifetime cannabis use declined by 17%. After accounting for alcohol and tobacco use the association between early sexual debut and cannabis was attenuated (AOR = 0.90, 95% CI = 0.68-1.20), while later age of debut remained protective (AOR = 0.57, 95% CI = 0.42-0.78). Results were generally consistent across race/ethnicity and gender.

CONCLUSIONS

Multifactorial intervention strategies targeting both sexual health and substance use may be warranted.

Tobacco smoking and cannabis use in a longitudinal birth cohort: evidence of reciprocal causal relationships

BACKGROUND

There is evidence of associations between tobacco and cannabis use that are consistent with both a classical stepping-stone scenario that posits the transition from tobacco use to cannabis use ('gateway' effect of tobacco) and with the reverse process leading from cannabis use to tobacco abuse ('reverse gateway' effect of cannabis). The evidence of direct causal relationships between the two disorders is still missing.

METHODS

We analysed data from the Christchurch Health and Development Study (CHDS) longitudinal birth cohort using advanced statistical modelling to control for fixed sources of confounding and to explore causal pathways. The data were analysed using both: (a) conditional fixed effects logistic regression modelling; and (b) a systematic structural equation modelling approach previously developed to investigate psychiatric co-morbidities in the same cohort.

RESULTS

We found significant (p<0.05) associations between the extent of cannabis use and tobacco smoking and vice versa, after controlling for non-observed fixed confounding factors and for a number of time-dynamic covariate factors (major depression, alcohol use disorder, anxiety disorder, stressful life events, deviant peer affiliations). Furthermore, increasing levels of tobacco smoking were associated with increasing cannabis use (p=0.02) and vice versa (p<0.001) over time.

CONCLUSIONS

Our results lend support to the notion of both of 'gateway' and 'reverse gateway' effects. That is, the association between tobacco and cannabis use arises from a reciprocal feedback loop involving simultaneous causation between tobacco use disorder and cannabis use disorder.

The therapeutic potential of cannabinoids for movement disorders

There is growing interest in the therapeutic potential of marijuana (cannabis) and cannabinoid-based chemicals within the medical community and, particularly, for neurological conditions. This interest is driven both by changes in the legal status of cannabis in many areas and increasing research into the roles of endocannabinoids within the central nervous system and their potential as symptomatic and/or neuroprotective therapies. We review basic science as well as preclinical and clinical studies on the therapeutic potential of cannabinoids specifically as it relates to movement disorders. The pharmacology of cannabis is complex, with over 60 neuroactive chemicals identified to date. The endocannabinoid system modulates neurotransmission involved in motor function, particularly within the basal ganglia. Preclinical research in animal models of several movement disorders have shown variable evidence for symptomatic benefits, but more consistently suggest potential neuroprotective effects in several animal models of Parkinson's (PD) and Huntington's disease (HD). Clinical observations and clinical trials of cannabinoid-based therapies suggests a possible benefit of cannabinoids for tics and probably no benefit for tremor in multiple sclerosis or dyskinesias or motor symptoms in PD. Data are insufficient to draw conclusions regarding HD, dystonia, or ataxia and nonexistent for myoclonus or RLS. Despite the widespread publicity about the medical benefits of cannabinoids, further preclinical and clinical research is needed to better characterize the pharmacological, physiological, and therapeutic effects of this class of drugs in movement disorders.

Prevalence of Cannabis Lifetime Use in Iranian High School and College Students: A Systematic Review, Meta-Analyses, and Meta-Regression

Cannabis is the most widely used substance in the world. This study aimed to estimate the prevalence of cannabis lifetime use (CLU) in high school and college students of Iran and also to determine factors related to changes in prevalence. A systematic review of literature on cannabis use in Iran was conducted according to MOOSE guideline. Domestic scientific databases, PubMed/Medline, ISI Web of Knowledge, and Google Scholar, relevant reference lists, and relevant journals were searched up to April, 2014. Prevalences were calculated using the variance stabilizing double arcsine transformation and confidence intervals (CIs) estimated using the Wilson method. Heterogeneity was assessed by Cochran's Q statistic and I(2) index and causes of heterogeneity were evaluated using meta-regression model. In electronic database search, 4,000 citations were retrieved, producing a total of 33 studies. CLU was reported with a random effects pooled prevalence of 4.0% (95% CI = 3.0% to 5.0%). In subgroups of high school and college students, prevalences were 5.0% (95% CI = 3.0% to -7.0%) and 2.0% (95% CI = 2.0% to -3.0%), respectively. Meta-regression model indicated that prevalence is higher in college students (β = 0.089, p < .001), male gender (β = 0.017, p < .001), and is lower in studies with sampling versus census studies (β = -0.096, p < .001). This study reported that prevalence of CLU in Iranian students are lower than industrialized countries. In addition, gender, level of education, and methods of sampling are highly associated with changes in the prevalence of CLU across provinces.

Cannabis controversies: how genetics can inform the study of comorbidity

AIMS

To review three key and controversial comorbidities of cannabis use-other illicit drug use, psychosis and depression, as well as suicide, from a genetically informed perspective.

DESIGN

Selective review.

RESULTS

Genetic factors play a critical role in the association between cannabis use, particularly early-onset use and use of other illicit drugs, psychosis and depression, as well as suicide, albeit via differing mechanisms. For other illicit drugs, while there is strong evidence for shared genetic influences, residual association that is attributable to causal or person-specific environmental factors cannot be ruled out. For depression, common genetic influences are solely responsible for the association with cannabis use but for suicidal attempt, evidence for person-specific factors persists. Finally, even though rates of cannabis use are inordinately high in those with psychotic disorders, there is no evidence of shared genetic etiologies underlying this comorbidity. Instead, there is limited evidence that adolescent cannabis use might moderate the extent to which diathesis influences psychosis.

CONCLUSIONS

Overlapping genetic influences underlie the association between early-onset cannabis use and other illicit drug use as well as depression and suicide. For psychosis, mechanisms other than shared genetic influences might be at play.

Chapter 5. Russian media narratives about young drug users

Since the 1960s, the media in Western Europe and the United States has been one important actor in the public understanding of the drug phenomenon. In Russia, however, it is only since the 1980s that illegal drugs have been discussed in the media and this discussion remains on-going today. By using narrative analysis, this article focuses on how illegal drug use among young people is constructed in the Russian press. As a result of the narrative analysis, three main discourses were identified: a foreign problem discourse, a disease discourse, and a medical discourse.

Marijuana: current concepts(†)

Marijuana (cannabis) remains a controversial drug in the twenty-first century. This paper considers current research on use of Cannabis sativa and its constituents such as the cannabinoids. Topics reviewed include prevalence of cannabis (pot) use, other drugs consumed with pot, the endocannabinoid system, use of medicinal marijuana, medical adverse effects of cannabis, and psychiatric adverse effects of cannabis use. Treatment of cannabis withdrawal and dependence is difficult and remains mainly based on psychological therapy; current research on pharmacologic management of problems related to cannabis consumption is also considered. The potential role of specific cannabinoids for medical benefit will be revealed as the twenty-first century matures. However, potential dangerous adverse effects from smoking marijuana are well known and should be clearly taught to a public that is often confused by a media-driven, though false message and promise of benign pot consumption.