Epidemiology of Youth Drug Abuse

Research Findings from September, 2000 Director's Report

This section lists selected summaries from NIDA funded research projects that investigate the epidemiology, etiology, and prevention research. The summaries provided were selected from recent issues of the Director's Report to the National Advisory Council on Drug Abuse. For a more comprehensive listing of NIDA funded projects see the Director's Report.

Gender Differences in Adolescent Drug Abuse: Issues of Comorbidity and Family Functioning

Dr. Gayle Dakof, University of Miami, investigated gender differences in patterns of co-morbidity and family functioning among a sample of 95 youths (42 girls) referred by juvenile justice (80%), education (10%) and social welfare (10%) for substance abuse treatment. Findings indicate that male and female adolescent substance users (13-17 years) entering treatment do differ. The girls not only used drugs and engaged in externalizing behaviors as extensively as did their male counterparts but they also were distinguished by their higher levels of internalizing symptoms and family dysfunction. Dakof, G. Journal of Psychoactive Drugs, 32(1), pp. 25-32, 2000.

Community Epidemiology Work Group

The 48th biannual meeting of the Community Epidemiology Work Group (CEWG), chaired by Mr. Nicholas J. Kozel, DESPR, was held in Baltimore, Maryland on June 13-16, 2000. The CEWG is composed of researchers from 21 metropolitan areas of the United States who meet semiannually to report on patterns and trends of drug abuse in their respective areas; emerging drugs of abuse; vulnerable populations and factors that may place people at risk of drug use and abuse; and, negative health and social consequences. Reports are based on drug abuse indicator data, such as morbidity and mortality information, treatment data and local and State law enforcement data. Additional sources of information include criminal justice, correctional, medical and community health data, local and State survey information and research findings from ethnographic studies. The following are highlights from the meetings:

IN THE PAST 6 MONTHS...

Cocaine indicators suggest declining or stable trends in most areas. Heroin indicators are mixed. Younger populations continue to initiate use in several cities, and some are shifting from snorting to injecting.

Marijuana indicators suggest continued elevated levels, with generally stable or mixed trends in most CEWG sites.

Methamphetamine consequences continue to decline in western and central CEWG sites; indicators remain low in the East but may be trending upward.

"Club drugs," especially GHB, GBL, MDMA, and ketamine, continue to spread across the country. MDMA availability is high and increasing in many CEWG areas, and its quality and content often varies widely.

Cocaine/Crack - Although some indicators increased slightly in a number of CEWG areas during the last reporting period, most cocaine indicators during this reporting period declined or were stable. Cocaine deaths1 were relatively stable, except in Detroit, where they decreased substantially, and Phoenix, where 1999 deaths outnumbered cumulative deaths for 1993-1998. After increasing in many sites during the last 6-month period, cocaine emergency department (ED) mentions2 decreased significantly in seven cities (Atlanta, Dallas, Chicago, New Orleans, New York, San Francisco, and Washington, DC). Nonsignificant ED decreases were reported in the majority of other cities; only two significant increases were noted (in St. Louis and Baltimore). Cocaine is the primary drug of choice for treatment admissions3 in six CEWG sites, excluding Baltimore where heroin and cocaine admissions are evenly distributed. Cocaine treatment and ED admissions tend to involve relatively older people, and the 35-and-older cohort seems to be increasing in many sites. Mixed trends were found in cocaine-positive urinalysis percentages4 among adult male arrestees, with increases at two sites (Dallas and Washington, DC), declines at three (Chicago, Los Angeles, Philadelphia), and stable trends at the rest; the drug is now surpassed by marijuana in all but six cities. By contrast, among female arrestees, cocaine is still the most commonly detected drug in all but one city (San Diego); levels increased in four cities (Chicago, Dallas, Minneapolis/St. Paul, and Phoenix) and declined in Los Angeles and Seattle. Speedball (crack combined with heroin) injections continue to be reported in some cities, including Baltimore, Boston, Denver, Miami, New York City, St. Louis, San Francisco, Seattle, and Washington, DC. High purity and greater availability of cocaine hydrochloride (HCl) may be driving the increase in HCl indicators in some sites, including Denver, Miami (among youth), Minneapolis/St. Paul, and Newark, and the decrease in crack indicators in some cities, such as Boston, Denver, Miami (possibly among youth), and Newark.

Heroin - Heroin indicators show mixed trends. Heroin mortality figures1 were mixed, with deaths increasing notably in three areas (Detroit, Minneapolis/St. Paul, and Phoenix), declining in two (Miami and Seattle), and stable in two. ED indicators2 were also mixed, with 10 cities showing decreases (2 significant-Miami and Baltimore) and 10 cities showing increases (2 significant-San Francisco and Washington, DC). Heroin is the predominant drug of choice among treatment admissions3 in three reporting sites, excluding Baltimore, where cocaine and heroin admissions are evenly distributed, and Seattle, where heroin and marijuana admissions are even distributed. Opiate-positive urinalysis levels4 among adult males remained relatively low (ranging from 3.4 to 20.1 percent-positive) and stable in most cities, except for Atlanta and Washington, DC, where opiate-positive levels increased, and in Philadelphia and Seattle, where levels declined. Conversely, among adult females, opiate-positive levels increased substantially in six cities (Chicago, Minneapolis/St. Paul, New Orleans, Phoenix, San Diego, and Washington, DC); they declined notably in Detroit. Heroin purity5 ranges from 10.7 percent in Miami to 72 percent in Philadelphia. Purity trended mostly upward or remained stable: increases were particularly steep in five cities (Detroit, Los Angeles, Newark, New Orleans, and Phoenix); a decline was notable in Denver (by 22.4 percentage points). Price trends were mixed. A troubling development is the continued reporting of increases of heroin use among young populations in many CEWG cities, including Atlanta (mostly white youth who snort), Baltimore, Boston (mostly young adults who inject and some high school students who snort), Chicago, Denver (youth who primarily snort or smoke), Detroit (suburban youth), Newark, Seattle (young injectors), and Washington, DC. In Boston, Chicago, Denver, Miami, and Washington, DC, snorting seems to be increasing and is often the initial route of administration for many young, new users; conversely, injecting is on an upward trend in Baltimore (among suburban youth), Boston (among youth), Minneapolis/St. Paul, Newark, New York City, and Seattle (among younger users), and many CEWG ethnographers note that heroin snorters often progress to injecting.

Marijuana - After several periods of increasing indicators, marijuana indicators are mixed or stable in most CEWG sites. Marijuana ED mentions2 increased significantly in three cities (Baltimore, Philadelphia, and Phoenix) and nonsignificantly in five others; they declined significantly in five cities (San Diego, San Francisco, New Orleans, Dallas, and Chicago) and declined nonsignificantly or remained level in seven cities. Marijuana is the predominant drug treatment problem3 in two areas (Colorado and Minneapolis/St. Paul), and in Seattle, heroin and marijuana admissions are evenly distributed. Treatment admissions-in particular, clients who use only marijuana-seem to be increasing in many CEWG areas. However, the proportion of marijuana treatment admissions referred by the criminal justice system is very high in most reporting areas when compared with other drug clients. Among adult male arrestees4, marijuana has now surpassed cocaine as the most commonly detected drug in the majority of CEWG cities. Positive findings continue to increase-sharply in six cities (Atlanta, Chicago, Los Angeles, Miami, Phoenix, and Seattle); and levels declined in three (Dallas, Philadelphia, and Washington, DC). Levels also increased or remained stable among female arrestees, except for one notable decline in Seattle. Juvenile arrestee levels exceeded adult marijuana-positive levels at all four sites where juveniles were tested. Marijuana blunts continue to be common in many CEWG areas, including Boston, Chicago (especially among African-American youth), New York City (especially among African-American youth), Washington, DC (especially among youth), and parts of Texas. Marijuana also continues as a delivery medium for other drugs: blunts are often laced with PCP ("3750s") in Chicago and with crack in Chicago, New York City, and parts of Texas. In Texas, marijuana/embalming fluid/PCP combinations are reported, and joints are sometimes dipped in codeine cough syrup. High-quality marijuana is available in most CEWG areas, and potency continues to increase in many.

Stimulants - Methamphetamine ("crystal meth," "ice") remains concentrated in the West and, to a lesser extent, in some rural areas elsewhere. In the West, most indicators continued showing the declines reported since 1998. Declining indicators are most likely related to low purity levels in some western and central sites and increased law enforcement attention; however, reports of manufacturers switching from the "cold method" to the "Nazi method" of production may warrant attention. The latter method produces high-purity methamphetamine, which may lead to future increased health consequences. (In San Diego, for example, purity increased in just the past few months.) In the East, methamphetamine indicators remain low, but ethnographic and law enforcement evidence continue to report slight increases in availability, especially in rural areas, among whites, and among youth at clubs, raves, and college parties. Methamphetamine ED mentions2 declined significantly in eight cities (Atlanta, Denver, Dallas, Chicago, New Orleans, Phoenix, San Diego, and San Francisco), decreased nonsignificantly in four cities, and increased nonsignificantly in only three cities (Philadelphia, St. Louis, and Boston). Methamphetamine remains the number-one primary drug problem among treatment admissions in Honolulu and San Diego3, although in San Diego most methamphetamine indicators continued to decline. Methamphetamine-positive percentages among adult male arrestees4 remained relatively low and stable, except in San Diego, where they declined notably; percentages among adult female arrestees increased notably in San Diego and Seattle and declined notably in Phoenix. In Seattle, youth are reportedly "mega-dosing" on pseudoephedrine, and in Texas, ephedrine abuse seems to be rising, especially among young adults.

Methylenedioxymethamphetamine (MDMA) ("ecstasy"), used primarily as a club drug at raves, dance clubs, and college scenes, is reportedly increasing in almost every CEWG city-an increase most likely driven by two factors: high availability due to large shipments from the Netherlands and other European countries; and the perception that it is a relatively harmless drug (known as the "hug drug" in Miami and the "love drug" in Minneapolis/St. Paul). In Boston and New York City, it seems to be spreading outside the club scene to the streets. Being under the influence of MDMA is referred to as "rolling" in cities across the Nation (including Chicago; Miami, where MDMA use is also referred to as "blowing up"; Minneapolis/St. Paul; and Washington, DC). In many cities, MDMA quality varies widely, and it frequently consists of entirely different substances, ranging from caffeine to dextromethorphan (DXM). For example, in Chicago, the ecstasy-like substance paramethoxyamphetamine (PMA) was involved in the deaths of two suburban youths who mistakenly thought the substance was true MDMA. In Washington, DC, where MDMA is taken by a wide range of age groups, some circular tablets are thought to be MDMA plus mescaline, some triangular tablets are thought to be heroin plus MDMA, and "nexus" tablets were verified by the DEA to be LSD plus MDMA. In Phoenix, a large quantity of high-quality MDMA, known as "candy canes" for their red and white stripes, was seized. Some older users in New York City prefer MDMA to cocaine because it lasts longer and is considered safer. Almost all cities reporting 1999 poison center data recorded an increase in MDMA-related calls since 1998. Most MDMA is taken orally in tablet form, but snorting has been reported (in Atlanta and Chicago), as has injecting (in Atlanta) and anal suppository (in Chicago). Methylphenidate (Ritalin) abuse may be increasing. Eight sites reported its abuse, primarily among youth who crush tablets and snort them, including Baltimore (among middle and high school students), Boston (especially in middle- and upper-class communities), Detroit (where one 14-year-old died in 1999 due to prolonged use, and where poison center calls are rising), Minneapolis/St. Paul, Phoenix, and parts of Texas. African-Americans on Chicago's South Side inject it, sometimes with heroin or heroin and cocaine. White injecting drug users (IDUs) in Chicago inject phenmetrazine (Preludin).

Depressants - Problems associated with rave and club drugs have risen dramatically in 1999. Gamma-hydroxybutyrate (GHB, a central nervous system depressant) and two of its precursors, gamma butyrolactone (GBL) and 1,4 butanediol (1,4 BDL, also called tetramethylene) have been increasingly involved in poisonings, overdoses, drug rapes and other criminal behaviors, or fatalities in nearly every CEWG city and their surrounding suburban and rural areas. These products, obtainable over the Internet and sometimes still sold in health food stores, are available at some gyms, nightclubs, raves, gay male party venues, on college campuses, or on the street. They are commonly mixed with alcohol, which may cause unconsciousness, have a short duration of action, and are not easily detectable on routine hospital toxicology screens. New esters and analogs of GHB continue to appear, even after Federal and State laws removed the sale of these drugs. In 1999, GHB accounted for 32 percent of illicit drug-related poison center calls in Boston-a number larger than that for MDMA. Conversely, in Chicago and San Francisco, GHB use is reportedly low compared with MDMA use, although GHB overdoses seem frequent compared with overdoses related to other club drugs. Even though it may be difficult to distinguish from water, several cities reported law enforcement indicators of GHB, including seizures of large amounts in Minneapolis/St. Paul and Phoenix. Withdrawal, addiction, and treatment indicators are emerging in several areas, including Miami and Minneapolis/St. Paul.

Use of the tranquilizer ketamine ("Special K" or "vitamin K"), also available and common in the club, rave, and party scene, is increasingly reported in numerous cities, including Atlanta, Baltimore (where users are predominantly white youth from middle- and upper-socioeconomic backgrounds), Boston (where some white, middle-class youth inject it, it is used as a heroin adulterant, and it may have been involved in some overdose deaths), Chicago (where it is available in powder form), Minneapolis/St. Paul (where injecting is reported), Newark, New York City (where it is available on the street, is either snorted or injected, and is sometimes mistaken for cocaine HCl), Phoenix, San Diego, Texas, and Washington, DC. In Detroit and St. Louis, veterinary break-ins for ketamine have increased in the past year. Clonazepam (Klonopin or Rivotril) and alprazolam (Xanax) use, in various combinations, is reported in Boston, where diverted prescription drug seizures have increased sharply after a recent rash of pharmacy break-ins. Those two drugs have replaced flunitrazepam (Rohypnol) among adolescents in Miami; similarly, in parts of Texas, clonazepam continues to replace flunitrazepam, especially in combination with beer. Flunitrazepam continues to be a problem among treatment admissions in Texas, particularly among young Hispanic males along the Mexican border, and it has been involved in numerous poison control calls. It also remains available in Atlanta, Minneapolis/St. Paul, and New Orleans. Recent deaths in Seattle have involved concomitant injection of heroin and a depressant, typically diazepam.

Hallucinogens-Lysergic acid diethylamide (LSD) ED mentions increased significantly in six cities (Baltimore, Detroit, Minneapolis/St. Paul, Phoenix, and Washington, DC); no significant declines were recorded. In several CEWG areas, LSD used in combination with other club drugs continues to be reported among youth. For example, in south Florida, "rolling and trolling," combining LSD and MDMA, continues. In Texas, MDMA dealers also sell LSD. In Minneapolis/St. Paul for the first time, LSD has been sold on soda crackers, and in Phoenix, it is sold in "Sweet Breath" (a breath freshener) dropper bottles. Phencyclidine (PCP) ED mentions were mixed, with two significant increases (in Chicago and Dallas) and two significant declines (in Miami and San Francisco). Among arrestees, PCP-positive findings remained generally stable, except for a decrease in Philadelphia and, following a decade of marked decline, an upturn in Washington, DC. The recent increases in the Dallas PCP indicators (including ADAM, ED, and poison center data) may reflect the use of marijuana cigarettes dipped in embalming fluid containing PCP. PCP continues to be smoked with marijuana in Chicago (known there as "wicky stick" or "donk"), Minneapolis/St. Paul, New York City, and St. Louis. In New York City, it is also sold as a liquid in small shaker bottles; in Phoenix, six deaths in 1999 were related to PCP. Psilocybin mushrooms ("shrooms") and mescaline are common among adolescents and young adults in Boston. Peyote is readily available in Phoenix. In 1999, Texas poison centers reported calls involving the hallucinogenic plants, morning glories.

Other drugs - Cough medicines with DXM are commonly abused ("robo tripping") by teens in Boston and Minneapolis/St. Paul, where DXM is reportedly also available as a powder in clear capsules. In Atlanta, inhalants are increasingly used among club goers; in Detroit, nitrous oxide and propane use continues to be reported; in Phoenix, several deaths involving inhalants occurred in 1999, and in Texas, poppers, spray paint, gas, glue, and freon are reportedly abused. Needle exchange personnel in areas surrounding Boston report steroid injection among young male body builders. In Atlanta, law enforcement sources note the potential for abuse of the anabolic steroid clenbuterol (Spiropent) by weight lifters.

Use of Case-Crossover Designs and Alternating Logistic Regression in Drug Abuse Studies

Researchers at Johns Hopkins University published two papers on methods for studying illicit drug use. The first deals with the use of the case-crossover design, which was developed to study time-varying exposures that cause transient excess risk of acute health events. It is a variant of case-control and subject-as-own- control research designs, involving use of information about exposure history of each case to estimate the transient effect. This kind of self-control design can help to reduce sampling bias otherwise introduced in the selection of controls, as well as confounding bias that might be derived from enduring individual characteristics, especially personality traits and other long-standing inherited or acquired vulnerabilities. When the subject is used as his or her own control, these personal vulnerabilities are matched. This paper discusses strengths and weaknesses of the case-crossover design and suggests applications of the case-crossover design in epidemiologic studies on suspected hazards of illicit drug use, and in studies of drug use and co-occurring psychiatric disturbances. The authors conclude that the case-crossover design can play a useful role, but it discloses a need to secure fine-grained measurements in epidemiologic research on psychiatric comorbidity. They also argue that this method may be of use to criminologists who study the drugs-crime nexus, to services researchers and clinicians who seek to understand treatment entry and compliance behavior, and to etiologists interested in polydrug use. The second article describes the alternating logistic regression (ALR) method and places this method in the context of other statistical approaches to the analysis of complex survey data, including the conditional form of logistic regression with matching on neighborhood characteristics. Unlike conditional logistic regression, the ALR method provides for an explicit estimation of the magnitude of clustering of drug use within neighborhoods and within subgroups of the neighborhood defined by male-female or age indicators, with and without covariate adjustments. The application of these ALR methods is illustrated with estimates for the magnitude of clustering of daily marijuana use and weekly marijuana use within neighborhoods of the United States, based on data from the National Household Survey on Drug Abuse samples from 1990 through 1996. (1) Wu, L.T. and Anthony, J.C. The Use of the Case-Crossover Design in Studying Illicit Drug Use. Substance Use & Misuse, 35(6-8), pp. 1035-1050, 2000. (2) Bobashev, G.V. and Anthony, J.C. Use of Alternating Logistic Regression in Studies of Drug-Use Clustering. Substance Use & Misuse, 35(6-8), pp. 1051-1073, 2000.

Developmental Taxonomy of Marijuana Users

This study applied cluster analysis to a community-based sample of marijuana users followed from adolescence to mid-30's, to create a taxonomy for marijuana use similar to those proposed for alcohol. Four groups with distinguishing characteristics emerged: early onset (age 15)-heavy use; early onset-light use; mid onset (age 16)-heavy use; and late onset (age 19.5)-light use. Of note, early onset of use did not in itself signify risk for later drug dependence; a concurrent psychiatric problem was strongly associated with risk for dependence in the early onset group, and absence of psychopathology distinguished the users who did not progress to heavy use. Association with marijuana-using peers and peer delinquency also distinguished those early users who progressed to heavy use. These findings add to our understanding about the course and risk for marijuana use, and make important distinctions among different typologies. Kandel, D.B., and Chen, K. Types of Marijuana Users by Longitudinal Course. Journal of Studies on Alcohol, 61, pp. 367-378, 2000.

Cross-national Comparisons of the Prevalences and Correlates of Mental and Substance Use Disorders

Researchers at Harvard University, other U.S. and foreign research institutions and the World Health Organization (WHO) have formed an International Consortium in Psychiatric Epidemiology (ICPE) in order to carry out cross-national comparative studies of the prevalences and correlates of mental disorders. This article describes the findings of surveys in seven countries in North America (Canada and USA), Latin America Brazil and Mexico), and Europe (Germany, Netherlands, and Turkey), using a version of the WHO Composite International Diagnostic Interview (CIDI) to generate diagnoses. The results are reported using DSM-III-R and DSM-IV criteria without diagnostic hierarchy rules for mental disorders and with hierarchy rules for substance-use disorders. Prevalence estimates varied widely--from >40% lifetime prevalence of any mental disorder in Netherlands and the USA to levels of 12% in Turkey and 20% in Mexico. Comparisons of lifetime versus recent prevalence estimates show that mental disorders were often chronic, although chronicity was consistently higher for anxiety disorders than for mood or substance-use disorders. Retrospective reports suggest that mental disorders typically had early ages of onset, with estimated medians of 15 years for anxiety disorders, 26 years for mood disorders, and 21 years for substance-use disorders. All three classes of disorders were positively related to a number of socioeconomic measures of disadvantage (such as low income and education, unemployed, unmarried). Analysis of retrospective age-of-onset reports suggest that lifetime prevalences had increased in recent cohorts, but the increase was less for anxiety disorders than for mood or substance-use disorders. Delays in seeking professional treatment were widespread, especially among early- onset cases, and only a minority of people with prevailing disorders received any treatment. The authors conclude that there is a need for demonstration projects of early outreach and intervention programs for people with early-onset mental disorders, as well as quality assurance programs to look into the widespread problem of inadequate treatment. Andrade, L., Caraveo-Anduaga, J.J., Berglund, P., Bijl, R., Kessler, R.C., Demler, O., Walters, E., Kylyc, C., Offord, D., Ustun, T.B., and Wittchen, H.U. Cross-national Comparisons of the Prevalences and Correlates of Mental Disorders. Bulletin of the World Health Organization, 78(4), pp. 413-426, 2000.

Initiation of Alcohol and Marijuana Use

Guided by the social development model, this study examined dynamic patterns and predictors of alcohol and marijuana use initiation. The sample was derived from a longitudinal study of 808 youth interviewed annually from 10 to 16 years of age and at 18 years of age. Rate of alcohol initiation rose steeply up to the age of 13 years and then increased more gradually; most participants had initiated by 13 years of age. Marijuana initiation showed a different pattern, with more participants initiating after the age of 13 years. The study showed that: (1) the risk of initiation spans the entire course of adolescent development; (2) young people exposed to others who use substances are at higher risk for early initiation; (3) proactive parents can help delay initiation; and (4) clear family standards and proactive family management are important in delaying alcohol and marijuana use, regardless of how closely bonded a child is to his or her mother. Kosterman R., Hawkins J.D., Guo J., Catalano R.F., and Abbott, R.D. The Dynamics of Alcohol and Marijuana Initiation: Patterns and Predictors of First Use in Adolescence. American Journal of Public Health, 90(3), pp. 360-366, 2000.

Ethnic and Gender Differences and Similarities in Adolescent Drug Behaviors

This study examined relationships among ethnicity, gender, drug use, and resistance to drug offers in a sample of 2,622 African American, Mexican American, and White American seventh graders. Findings included: first, the adolescents did not possess large or sophisticated repertoires of drug resistance strategies. Second, most offers came from acquaintances in contrast to data on older adolescents where offers generally come from intimate friends. Third, ethnicity had significant effects on use and the offer process. Mexican Americans received more offers, used more drugs, and were more likely to be offered drugs by peers, family members and at parties. European Americans were more likely to receive drug offers from acquaintances and at friends' homes and on the street. African Americans were more likely to receive offers from dating partners and parents, and in the park, and were more likely to resist offers of drugs-using explanations. Fourth, gender significantly affected drug offers and types of offers. Males were more at risk for offers and use at a younger age. Offers of drugs to males were more likely to come from parents or other males, while offers to females were more likely to come from other females or dating partners. Males were also more likely to receive drug offers that appealed to their social standing or self-image whereas females received either simple offers or those that minimize effects. Finally, offers of drugs to males were more likely to be made in public, while those to females were more likely to occur in private. Moon, D.G., Hecht M.L., Jackson, K.M., and Spellers R.E. Ethnic and Gender Differences and Similarities in Adolescent Drug Use and Refusals of Drug Offers. Substance Use and Misuse. 34 (8), pp. 1059-1083, 1999.

Peer Behavioral Assessments Predict Later Problems

This study assessed whether peer-ratings of behavioral reputation predicted teacher-rated behavioral adjustment and academic achievement four years later. In a prospective, longitudinal design with a community sample of 213 disruptive and 104 nondisruptive children, peers were asked to assess behavioral reputation. Regression analyses showed that peer ratings of aggressive-disruptive, sensitive-isolated, and social etiquette behaviors were the best predictors of later externalizing and internalizing problems and adaptive skills, respectively. The peer-rated problematic behaviors continued to be related to these outcomes, even when parent and teacher ratings of behavior problems at baseline were included in the equation with peer ratings. However, behavioral reputation was not related to academic achievement. Realmuto, G.M., August, G.J., and Hektner, J.M. Predictive Power of Peer Behavioral Assessment for Subsequent Maladjustment in Community Samples of Disruptive and Nondisruptive Children. Journal of Child Psychology and Psychiatry and Allied Disciplines 41(2), pp. 181-190, 2000.