Studies Of Substance Use Research Articles

Measurement issues in race ethnicity and substance use

ABSTRACT Objective To investigate substance use patterns by race and ethnicity with more detail about racial and ethnic background. There are many studies of substance use and race-ethnicity, however few studies have examined a more diversified delineation of race and ethnicity. By looking more closely at racial and ethnic groups who are multiracial and multiethnic, we may gain more information about patterns of substance use among diverse groups of people in the United States. Methods We use national data sample from the United States and delineate racial and ethnic groups. Results Findings indicate that there are substantive differences in patterns of substance use among the race, ethnic and multiracial/ethnic populations in the United States. These patterns vary by substance used and strongly suggest that we need a careful assessment of the measurement used to classify individuals as racial and ethnic people in our studies. Conclusions The measurement of racial and ethnic groups should be more fully assessed since the patterns of substance vary considerably within traditionally measured racial and ethnic groups.

Improving in-depth, epidemiological and economic understanding of substance use, harm and its prevention across countries

Welcome to the second issue of Volume 8 of IJADR for 2020. This issue includes papers that focus on the global burden of different substances and their costs as well as studies of substance use and related harm by authors in Scandinavia and North America. The five papers include qualitative and quantitative studies and involve diverse populations from Canada, Sri Lanka, Germany and the United States. In an attempt to identify substance use research priorities for Canada, Sornpaisarn and colleagues (2020) reviewed 2014-2019 publications and analysed secondary data sources to study the relative substance-attributable burden of disease for alcohol, tobacco and other drugs in Canada, finding that tobacco followed by other drugs contributed more to the burden of disease estimates than did alcohol. This pattern was also evident in North America and differs considerably from that observed in the overall global burden of disease estimates, where alcohol ranks higher than other drugs in terms of its contribution to GBD. Secondly, this article reported on wholly attributable relative substance use disorder diagnoses in Canada, finding that relative to alcohol, opioid use disorders required more admissions to hospital. Finally, this article highlights that the greatest societal costs tallied in 2014 were for the costs of alcohol, followed by tobacco and all other drugs combined. Both other drug use and alcohol diagnosis costs increased in the period between 2007 and 2014, with cannabis and opioid costs increasing and tobacco costs declining. Leifman and Trolldal (2020) undertook an interesting study of price and income elasticity in Sri Lanka, finding that the economic drivers of alcohol sales appeared not to be affected by price and income changes to the same extent as sales in high-income countries or in the few studies that have been undertaken in other low- and middle-income countries. Their paper discusses aspects of Sri Lankan drinking culture including limitations on women’s drinking, the greater prevalence of lighter drinking and abstinence, banning of drinking on public holidays and drinking by tourists that may explain why general patterns of alcohol sales are less affected by price and income than expected, but argues that further research is needed to understand drivers of consumption in Sri Lanka. In a study among sexual minority and non-sexual minority men and women in the United States, Karen Trocki and her colleagues (2020) examined the extent to which the protective effects of marriage on substance use that are commonly observed among heterosexual men and women apply to sexual minority groups. They found that marriage confers protective effects against substance use depending on individuals’ sexual minority or non-sexual minority status, their sex, and the substances under study. The researchers call for further research to unpack the factors that may explain the role of marriage as a protective factor against substance use in sexual minority individuals. Egerer and Hellman’s (2020) study considered techniques that may be employed for interpreting researchers’ subjectivity – a well-recognized element – in qualitative research. They introduced three techniques: a form of content analysis, quantification of researchers’ expectations, and analysis of speaker positions among study participants. Using examples of data from focus groups among social workers in Germany, the paper discusses some of the contrasting impressions of qualitative data that can emerge from the use of the different techniques. This paper is likely to be very informative for many readers, and particularly, for those who may not be familiar with methods of analyzing and interpreting qualitative data. Using multi-level data, Julie Croff and her colleagues (2020) examined the extent to which individual-level and school-level parental factors, school environmental factors, alcohol, tobacco and other drug (ATOD) descriptive norms and peer deviance are associated with early adolescents’ lifetime alcohol consumption in a study conducted among seventh grade students in the United States of America. They found that parents’ educational involvement and peer deviance at both the individual and school levels were associated with the adolescents’ alcohol use; however, only individual level ATOD norms were associated with lifetime alcohol use. A key implication of the findings concerns the role of parental involvement at the school level in early adolescents’ alcohol use. The authors concluded that “Parent educational engagement programs need not target all parents, as strong results at the school level may come from a core team of key parent leaders.” (page 93).

Mechanical Turk data collection in addiction research: utility, concerns and best practices.

Amazon Mechanical Turk (MTurk) provides a crowdsourcing platform for the engagement of potential research participants with data collection instruments. This review (1) provides an introduction to the mechanics and validity of MTurk research; (2) gives examples of MTurk research; and (3) discusses current limitations and best practices in MTurk research. We review four use cases of MTurk for research relevant to addictions: (1) the development of novel measures, (2) testing interventions, (3) the collection of longitudinal use data to determine the feasibility of longer-term studies of substance use and (4) the completion of large batteries of assessments to characterize the relationships between measured constructs. We review concerns with the platform, ways of mitigating these and important information to include when presenting findings. MTurk has proved to be a useful source of data for behavioral science more broadly, with specific applications to addiction science. However, it is still not appropriate for all use cases, such as population-level inference. To live up to the potential of highly transparent, reproducible science from MTurk, researchers should clearly report inclusion/exclusion criteria, data quality checks and reasons for excluding collected data, how and when data were collected and both targeted and actual participant compensation. Although on-line survey research is not a substitute for random sampling or clinical recruitment, the Mechanical Turk community of both participants and researchers has developed multiple tools to promote data quality, fairness and rigor. Overall, Mechanical Turk has provided a useful source of convenience samples despite its limitations and has demonstrated utility in the engagement of relevant groups for addiction science.

Alcohol and drug use among staff at licensed premises in Norway.

There is increased concern about the use of alcohol and illicit drugs in nightlife settings. Most studies of substance use in nightlife settings are from the patrons' perspective, which leaves an understudied population - the nightclub staff. The aim of this paper is to study self-reported alcohol and substance use among staff at licensed premises in Norway: types of illicit drugs used, attitudes towards drugs, and observed drug use among patrons. A survey was conducted at server-training courses in 20 different cities in Norway during 2015. The survey included: demographics, respondents' own alcohol and drug experience, attitudes towards drug use, and observed drug use among patrons at licensed premises. Data were collected from 912 staff working at licensed premises. A majority reported alcohol use in the past year, and 61% reported alcohol use two or more times a month. Overall, 45% of the respondents reported ever-used of illicit drugs. The four most commonly used drugs among staff were cannabis, cocaine, ecstasy/MDMA, and amphetamine. The majority of respondents supported Norway's strict drug laws, and 63% reported observing drug-intoxicated patrons at licensed premises during the past six months. The proportion of frequent drinkers and heavy episodic drinking among staff at licensed premises was high, and the prevalence of illicit drug use was much higher compared with the general population. Thus, staff at licensed premises can be considered a risk-group for alcohol and illicit drug use and therefore represent an important target population in club drug-prevention programmes.

Genetic variation in the exome: Associations with alcohol and tobacco co-use.

Shared genetic factors represent one underlying mechanism thought to contribute to high rates of alcohol and tobacco co-use and dependence. Common variants identified by molecular genetic studies tend to confer only small disease risk, and rare protein-coding variants are posited to contribute to disease risk, as well. However, given that genotyping technologies allowing for their inclusion in association studies have only recently become available, the magnitude of their contribution is poorly understood. The current study examined genetic variation in protein-coding regions (i.e., the exome) for associations with measures of lifetime alcohol and tobacco co-use. Participants from the UCSF Family Alcoholism Study (N = 1,862) were genotyped using an exome-focused genotyping array, and assessed for DSM-IV diagnoses of alcohol and tobacco dependence and quantitative consumption measures using a modified version of the Semi-Structured Assessment for the Genetics of Alcoholism. Analyses included single variant, gene-based, and pathway-based tests of association. One EMR3 variant and a pathway related to genes upregulated in mesenchymal stem cells during the late phase of adipogenesis met criteria for statistical significance. Suggestive associations were consistent with previous findings from studies of substance use and dependence, including variants in the CHRNA5-CHRNA3-CHRNB4 gene cluster with cigarettes smoked per day. Further, several variants and genes demonstrated suggestive association across phenotypes, suggesting that shared genetic factors may underlie risk for increased levels of alcohol and tobacco use, as well as psychopathology more broadly, providing insight into our understanding of the genetic architecture underlying these traits. (PsycINFO Database Record

Differential effects of sex on substance use between first episode psychosis patients and healthy people

BackgroundSubstance use in psychosis is an important field of study given that it can be a risk factor for the development of psychosis and can give rise to psychotic symptoms. Studies of substance use in first episode psychosis patients do not frequently assess non-pathological substance consumption among patients, but rather the prevalence of substance abuse or dependence disorders. Moreover, most of these studies do not address the effects of sex in sufficient depth, and the consumption of caffeine or tobacco, which are two of the most frequently used substances, is often not assessed. ObjectivesThe aim of this study was to compare patterns and quantities of substance use between first episode psychosis patients and healthy controls and between men and women, and explore the potential interactive effects between group (patients or controls) and sex. MethodsA total of 158 participants (82 first episode psychosis patients and 76 healthy controls) were included in the study. Both adults and adolescents were included in the study. Frequency and amount of use of caffeine, tobacco, alcohol, cannabis, cocaine, hallucinogens, stimulants, and opiates were gathered. ResultsA significant main effect of sex was found for the frequency of use of tobacco (p=.050). Main effects of group were found for the quantity of tobacco (p<.001) and cannabis (p<.001) consumed, as well as main effects of sex for the quantity of alcohol (p=.003) and cannabis (p=.017) consumed. There were also interaction effects between group and sex for the frequency of use of tobacco (p=.005) and cannabis (p=.009), and for the amount of cannabis consumed (p=.049). Qualitative differences between males and females regarding combined substance use are also reported. ConclusionsAmong patients, men used tobacco more frequently than women, but this sex difference was not the same for the control group, in which women smoked more often than men. Regarding cannabis, men smoked cannabis more frequently and in larger amounts than women, but only in the patients group, whereas no sex differences for cannabis were found for the controls. Main effects of group and sex for tobacco and alcohol, as well as the lack of differences for the frequency and amount of use of caffeine, are also commented. This is the first study to assess the different effects of sex on substance use in first episode psychosis patients and healthy controls.

Substance Use Patterns Through Early Adulthood: Results for Youth With and Without Chronic Conditions.

Adolescence and emergent adulthood are periods of peak prevalence for substance use that pose risks for short- and long-term health harm, particularly for youth with chronic medical conditions (YCMC) who are transitioning from adolescence to adulthood. As there have been no nationally representative studies of substance use during this period for these medically vulnerable youth, the authors sought to examine onset and intensification of these behaviors for a national sample of youth with and without chronic conditions. Longitudinal data are from 2,719 youth between the ages of 12 and 26 years interviewed from 2002 to 2011 for the Panel Study of Income Dynamics, Child Development and Transition to Adulthood Supplements, a nationally representative, population-based survey. Multivariate generalized linear mixed models were used to estimate patterns of alcohol, tobacco, and marijuana use during adolescence and emergent adulthood for youth with and without chronic conditions, adjusting for potential confounders. Overall, 68.8%, 44.3%, and 47.8% of youth reported ever trying alcohol, tobacco, and marijuana, respectively. Among users, 42.2%, 73.4%, and 50.3% of youth reported binge drinking, regular cigarette use, and recent marijuana use, respectively. YCMC were more likely to engage in any and heavier substance use; transition years and early adulthood were periods of peak risk for YCMC compared with their healthy peers. Substance use among YCMC during adolescence and emergent adulthood is a substantial concern. Increased prevention and case detection are in order to address these behaviors and promote optimal health outcomes for medically vulnerable youth.

Substance use among Dutch homeless people, a follow-up study: prevalence, pattern and housing status.

Previous studies have shown that substance use among homeless people is a prevalent problem that is associated with longer durations of homelessness. Most studies of substance use among the homeless were carried out outside Europe and have limited generalizability to European countries. This study therefore aimed to address the prevalence of substance use among homeless people in the Netherlands, the pattern of their use and the relationship with housing status at follow-up. This study included 344 participants (67.1% of the initial cohort) who were followed from baseline to 18 months after the baseline interview. Multinomial logistic regression analyses examined the relationship between substance use and housing status. The most reported substances which were used among these homeless people were cannabis (43.9%) and alcohol (≥5 units on one occasion) (30.7%). Other substances were used by around 5% or less of the participants. Twenty-seven percent were classified as substance misuser and 20.9% as substance dependent. The odds to be marginally housed (4.14) or institutionalized (2.12) at follow-up compared to being housed of participants who were substance users were significantly higher than those of participants who did not use substances. The odds to be homeless were more than twice as high (2.80) for participants who were substance dependent compared with those who were not. Homeless people who use substances have a more disadvantageous housing situation at follow-up than homeless people who do not use substances. Attention is needed to prevent and reduce long-term homelessness among substance-using homeless people.

Can we predict retention in longitudinal studies of substance use? Findings from the Australian Treatment Outcome Study

BackgroundLongitudinal studies are often threatened by difficulties with sample attrition, high rates of which threaten the validity of study findings. The present study examined methodological and participant characteristics associated with sample retention in the Australian Treatment Outcome Study (ATOS) across 3years. MethodFollow-up interviews were conducted at 3-, 12-, 24-, and 36-months post baseline, with follow-up rates of 89%, 81%, 76% and 70%, respectively. Structured interviews measuring past-month drug use, mental health, criminal involvement and demographic characteristics were administered to participants at baseline and each follow-up. Data were analysed using multinomial logistic regression and generalised estimating equations to produce odds ratios with 95% confidence intervals. ResultsCompleting all follow-up interviews was associated with being in treatment (OR 3.62), using other opiates at baseline (OR 3.45), more years of schooling (OR 1.20), and having completed the previous interview (OR 35.04). A history of incarceration was independently associated with not completing follow-up interviews (OR 0.47). ConclusionRetention can largely be predicted at study entry, and is unaffected by changes that occur in the interim. These findings highlight the importance of obtaining and maintaining comprehensive locator information, maintaining strong relationships with treatment agencies, as well as the necessity of patience, perseverance and flexibility.

Substance Abuse Among Prisoner in Erbil/Iraq

Background and objectivesLarge proportions of people who enter the criminal act andprison have a history of drug use. Many of these people continue to use drugswhile in prison. As there havebeen no recent studies of substance use in prisoners among our community, wehave conducted this study of the prevalence of substanceabuse and dependence in prisoners. MethodsThis study was conducted atdirectorate of adult reformatory prison in Erbil city, within a period of 6months between 15th of March to 15 September 2014. A convenient sample of 100sentenced male prisoners from the entire number during the period of the studywas selected. After randomization each prisoner was assessed throughsemi-structured interview based on the DSM IV. Drug abuse patterns and the relationship among addiction, crimeprevalence, and some personal as well as socio-demographic characteristics werestudied. ResultsAccordingto the findings, characteristics such as age, education level, economic status, urban and/or rural status, all have an effects on the rate of drug use and, oncrime commitment and its re-occurrence. Accordingly, younger age, lowersocioeconomic status and urban residence showed a relationship with tendency tocommit crime. ConclusionThe prevalence of substance abuse anddependence, although highly variable, is typically many orders of magnitudehigher in prisoners than the general population. This highlights the need forscreening for substance abuse and dependence at reception into prison, effective treatment while in custody, and follow-up on release.

Genome-Wide Association Studies of Substance Use: Considerations Regarding Populations and Phenotypes

Genome-wide association studies (GWAS), such as the study by Gelernter et al. (1) in the present issue, have yielded several important advances in the identification of genetic variants influencing risk for psychiatric disorders. For example, large-scale meta-analytic studies of smoking-related traits have reported genome-wide significant evidence of associations between smoking quantity and nicotine dependence and the chromosome 15 nicotinic receptor gene cluster, CHRNA5-CHRNA3-CHRNB4, and other genes related to nicotine metabolism (2).

Epidemiology of substance use disorders

Epidemiological studies of substance use and substance use disorders (SUDs) have provided an abundance of data on the patterns of substance use in nationally representative samples across the world (Degenhardt et al. in PLoS Med 5(7):e141, 2008; Johnston et al. in Monitoring the future national survey results on drug use, 1975-2010, vol I, secondary school students. Institute for Social Research, Ann Arbor, MI, 2011; SAMHSA in Results from the 2010 national survey on drug use and health: summary of national findings, vol NSDUH, series H-41, HHS Publication No. (SMA) 11-4658. Substance Abuse and Mental Health Services Administration, Rockville, 2011). This paper presents a summary of the goals, methods, and recent findings on the epidemiology of substance use and disorders in the general population of adults and adolescents and describes the methods and findings on the genetic epidemiology of drug use disorders. The high 12-month prevalence rates of substance dependence in US adults (about 12% for alcohol and 2-3% for illicit drugs) approximate those of other mental disorders as well as chronic physical disorders with major public health impact. New findings from the nationally representative samples of US youth reveal that the lifetime prevalence of alcohol use disorders is approximately 8% and illicit drug use disorders is 2-3% (Merikangas et al. in J Am Acad Child Adolesc Psychiatry 49(10):980-989, 2010; Swendsen et al. in Arch Gen Psychiatry 69(4):390-398, 2012; SAMHSA in Results from the 2010 national survey on drug use and health: summary of national findings, vol NSDUH, Series H-41, HHS Publication No. (SMA) 11-4658. Substance Abuse and Mental Health Services Administration, Rockville, 2011). The striking increase in prevalence rates from ages 13 to 18 highlight adolescence as the key period of development of SUDs. The application of genetic epidemiological studies has consistently demonstrated that genetic factors have a major influence on progression of substance use to dependence, whereas environmental factors unique to the individual play an important role in exposure and initial use of substances. Identification of specific susceptibility genes and environmental factors that influence exposure and progression of drug use may enhance our ability to prevent and treat SUDs.

Factors associated with missing data in an experience sampling investigation of substance use determinants

Background The Experience Sampling Method (ESM) collects data repeatedly over time, and is therefore prone to missing observations. Little is known about the characteristics of the subjects and of the ESM procedure associated with unanswered records. Through an ESM investigation of substance use determinants, these characteristics were able to be analyzed. Methods Participants ( n = 224) were undergraduate university students enrolled for a study of substance use factors, providing data through the use of classic questionnaires and through the Experience Sampling Method (ESM) using palmtop computers. For the ESM, they were signaled five times per day for 7 days (7840 records). Characteristics of the ESM procedure and of the participants were analyzed jointly. The probability of an unanswered ESM record was analyzed using a random-intercept logistic regression, fitting a multivariate mixed-effect model for repeated measurements. Results Factors significantly associated with an unanswered record were: male gender, being a Sport Science student, having higher scores of novelty seeking and of persistence, and being a poly-substance user. Unanswered records were also more frequent in the middle of the week and at the beginning of the day. Conclusion Findings are discussed in term of the possible impact of missing observations. In particular, the lower compliance of poly-substance users with the ESM protocol may curtail the validity of the method, since ESM records are less representative of all moments in these persons daily life. Thus, results from ESM studies of substance use should be regarded cautiously and complemented with other data gathering procedures.

Substance Use Among Adolescents with Type 1 Diabetes

Purpose: Adolescents with diabetes are as likely to engage in risky behaviors as healthy adolescents. Substance use in particular can adversely affect their ability to manage their diabetes and overall health. In the adult diabetic population, smoking is found to be highly correlated with diabetes mismanagement, leading to higher morbidity and mortality in later life. However, prospective studies of substance use among youth with Type 1 Diabetes are lacking. The limited available evidence is inconclusive about whether a relationship exists between substance use and glycemic control among youth with Type 1 Diabetes.

Ecological momentary assessment (EMA) in studies of substance use.

Ecological momentary assessment (EMA) is particularly suitable for studying substance use, because use is episodic and thought to be related to mood and context. This article reviews EMA methods in substance use research, focusing on tobacco and alcohol use and relapse, where EMA has been most applied. Common EMA designs combine event-based reports of substance use with time-based assessments. Approaches to data organization and analysis have been very diverse, particularly regarding their treatment of time. Compliance with signaled assessments is often high. Compliance with recording of substance use appears good but is harder to validate. Treatment applications of EMA are emerging. EMA captures substance use patterns not measured by questionnaires or retrospective data and holds promise for substance use research.

Lack of Gender Differences in Lifetime Substance Use Reported Among African-American Urban Community College Students

The purpose of this study was to examine whether there are significant gender differences concerning lifetime prevalence of substance use reported among a group of African-American urban community college students. Although gender differences have commonly been examined in studies of substance use and abuse, it appears that gender similarities may be more significant, including substance abusers and treatment. The interaction between gender and ethnicity is also more complex than generally acknowledged. Respondents completed sections of the Student Drinking Information Scale, the Family History of Alcoholism Scale, and the Khavari-Douglass Psychotropics Questionnaire. Lifetime prevalence was examined respectively for alcohol, tobacco, marijuana, cocaine, amphetamines, barbiturates, relaxants, and opiate drugs. The only substance category where a significant difference was observed between males and females was in reference to opiates. There was also no significant difference between the males and females in this sample with respect to reported family history of alcoholism. This general lack of observed gender difference in lifetime substance use suggests that addiction studies must more closely investigate this area of gender and ethnicity for more meaningful distinctions. This discussion will consider gender differences in substance use, gender differences and treatment, and interactions of gender and ethnicity and then will examine gender similarities with respect to substance use and abuse and, more specifically, gender similarities in substance abusers and treatment. Next follows an overview of methods, which includes procedures and instrumentation, the results of the study will be presented, and will be followed by a few concluding comments.

Prevalence of recent illicit substance use and reporting bias among MSM and other urban males

This paper explores whether elevated rates of self-reported substance use among MSM compared to other males may be an artifact of reporting bias. Past month prevalence rates of marijuana, cocaine, heroin, methamphetamine, Ecstasy, and Ketamine use were compared between a sample of men who have sex with men (MSM), and a general household sample of men, all residing in Chicago. We compared rates of self-reported use, and corrected rates based on the results of drug testing (urine and oral fluid tests). While MSM over 30 years old were significantly more likely than other men in this age group to report past month use of cocaine, test-corrected rates of use were equivalent. On the other hand, test-corrected estimates confirmed elevated rates of Ketamine and Ecstasy use in the MSM sample. Differential disclosure of substance use between MSM and other males may in some cases lead to distorted conclusions about differences in substance use between these groups. The use of biological testing in epidemiological studies of substance use can reduce the uncertainty of such comparisons.

Some costs and challenges of conducting follow-up studies of substance use in remote Aboriginal communities: an example from the Northern Territory

The objective of this study was to describe some costs and challenges for conducting follow-up interviews about substance use in Indigenous groups in northern Australia. In a remote region in the Northern Territory in 2001, 131 Indigenous people (aged 13 - 36 years) were approached for interview regarding their substance use. Of these, 108 (54 males, 54 females) were interviewed successfully. Follow-up interviews were attempted in 2004. Study records traced progress and costs. In 2001, the response rate was 82% (108/131). In 2004, 22 participants could not be found after four attempts although they were known by health workers to still reside in the region. Fifteen were not residing in the region during 2004 and were lost to follow-up, four were in prison and three were deceased. Fourteen contacted either refused directly (n = 1) or repeatedly postponed interview (n = 13). Fifty follow-up interviews were completed, a response rate of 78% among 64 participants contacted. The overall response rate in those approached was 64% (0.82 * 0.78). Costs for 108 interviews were 45 person-days and Dollars A19,000 (32% = travel/associated costs). Costs for 50 follow-up interviews were 60 person-days and Dollars A25,500 (39% = travel/associated costs). Such follow-up studies in these settings could be complemented by retrospective case - control approaches and by using proxy respondents to increase study efficiency.

Social Anxiety, Negative Affectivity, and Substance Use Among High School Students.

The literature regarding the relationship between adolescent social anxiety and substance use is sparse, and available studies have produced discrepant results. Similarly, negative affectivity is a mood-dispositional dimension that is infrequently considered in studies of substance use. The authors used dispositional structural equation modeling to examine the concurrent relationships of social anxiety and negative affectivity with adolescent substance involvement among 724 students in 1 southern California high school. The final model indicated that increased substance use was associated with having lower grade-point average, being male, being White, having higher levels of negative affectivity, and having lower levels of social anxiety. The findings confirm that negative affectivity is positively related to adolescent substance use, whereas social anxiety appears to be protective against substance involvement.

Genetic analysis workshop 13: Summary of analyses of alcohol and cigarette use phenotypes in the Framingham Heart Study.

Data from the Framingham Heart Study were provided for Genetic Analysis Workshop 13. This paper summarizes six contributed papers that focused on the analysis of the longitudinal alcohol and/or cigarette use phenotypes available in these data, with the goal of detecting genes influencing these traits. For several of these contributions, the primary phenotype was maximum daily substance use reported over the longitudinal data. Others focused on a cross section by taking the daily use reported at a fixed time interval for all individuals, and others considered dichotomous phenotypes defined by thresholds of use. A variety of covariates were considered, including age (or year of birth) and sex. Most studies included unexposed individuals (those reporting no alcohol/cigarette use at all available assessments) in the linkage analyses, though one study compared results when defining the phenotype for unexposed individuals to be zero vs. defining the phenotype for unexposed individuals to be unknown. Linkage findings varied across studies. However, there was some concordance of evidence on chromosome 9 for alcohol traits, and of weaker evidence on chromosome 20 for cigarette traits. Analytical issues arose which may be crucial for genetic studies of substance use and dependence, including the choice of how to handle unexposed or substance-naive individuals, use of dichotomous vs. quantitative traits, and consideration of transformations and covariates.