ELSEVIER Drug and Alcohol Dependence 45 (1997) 185- 196 Sequence of drug use among serious drug users: typical vs atypical progression Mary Ellen Mackesy-Amiti a,*, Michael Fendrich a, Paul J. Goldstein b ” Institute for Juvenile b School Research, of‘ Public Department Health, of Psychiatry, The University The University of Illinois at Chicago, 907, South IL 60612, USA of Illinois at Chicago, 2121 West Taylor Street, Chicago, Wolcott IL Avenue, 60612. Chicago. USA Received 13 August 1996; accepted 7 February 1997 Abstract Sequence of drug use was examined in a secondary analysis of two samples of serious drug users: one of 152 men and one of 133 women. The proportions of drug users following specified patterns of drug use onset were compared to proportions obtained in previous research in samples of high school youth, and serious drug users. The serious drug users were substantially different from high school samples in their progression of drug use. The serious drug users were less likely to follow the typical sequence identified in previous studies (alcohol, then marijuana, followed by other illicit drugs). They were more likely to have used marijuana before using alcohol, and more likely to have used other illicit drugs before using marijuana. We also found that atypical sequencing was associated with earlier initiation of the use of illicit drugs other than marijuana and greater lifetime drug involvement. These findings suggest that for a large number of serious drug users, marijuana does not play the role of a ‘gateway drug’. We conclude that prevention efforts which focus on alcohol and marijuana may be of limited effectiveness for youth who are at risk for serious drug abuse. 0 1997 Elsevier Science Ireland Ltd. Keywords: Secondary analysis; Marijuana; Alcohol; Gateway drug; Prevention efforts 1. Introduction A growing body of research has described developmental stages of drug use behaviour from adolescence through young adulthood. In general, researchers have found that adolescents tend to use alcohol and/or cigarettes before using marijuana and alcohol and marijuana prior to using other illicit drugs (e.g. Andrews et al., 1991; Brook et al., 1982; Donovan and Jessor, 1983; Kandel, 1980; Kandel and Faust, 1975; Kandel and Yamaguchi, 1993; Welte and Barnes, 1985; Yamaguchi and Kandel, 1984a,b). The same progression has been found in samples of youth in other countries (Adler and Kandel, 1981; Blaze-Temple and Lo, 1992). Guttman scale models have generally been found to fit about 85-90% of the cases. * Corresponding author Although there is variation across studies, particularly as to the importance and place of cigarettes in the sequence, there are two consistent findings. The majority of adolescents who use marijuana have also used alcohol and nearly all adolescents who use illicit drugs other than marijuana have also used marijuana. The proportions of subjects who used other illicit drugs prior to (or without any) marijuana use are for the most part less than 5%. Most of the drug users in a typical sample of high school students could be described as ‘occasional’ or ‘experimental’ drug users. The majority of those who report using illicit drugs, especially illicit drugs other than marijuana, say that they used the drugs only a few times in their lifetimes. For example, while 6.1% of 12th grade students in the 1992 Monitoring the Future study said that they used cocaine, 2.8% said they used only once or twice, while only 1.7O/o said they used 10 or 0376-8716/97/$17.00 0 1997 Elsevier Science Ireland Ltd. All rights reserved. PII SO376-8716(97)00032-X IX6 M.E. Mackay-Amiii rt al. /Drug and Alcoiml more times (Johnston et al.. 1993). While the typical sequence of use onset (i.e. alcohol, followed by marijuana, followed by other illicit drugs, hereafter abbreviated as A-M-O) may be characteristic of samples consisting mainly of occasional or experimental drug users. there is no clear evidence that it is characteristic of samples of serious drug users. By serious drug use, we mean that the drug use occupies a substantial portion of a person’s daily behaviour-including activities to raise money to buy the drugs and efforts to procure the drug, as well as drug consumption-over an extended period of time (see Goldstein et al., 1992; Johnson et al., 1985). Youths who are on their way to becoming serious drug users are more likely to drop out of school, or to be truant, and therefore are less likely to be captured in a survey of high school students (Oetting and Beauvais, 1990). Studies that report mean ages of first use of various substances suggest that narcotics users also follow the A-M-O sequence (Inciardi and Pottieger, 1986; 1991). That is. the mean age of first alcohol use was lower than that of first marijuana use and the mean age of first marijuana use was lower than that of any other illicit drug. However, these numbers do not tell the whole story; these studies did not look at the actual sequence of use onset, or the prevalence of different sequential patterns. Other studies provide some evidence that serious drug users are less likely to follow the typical sequence of use compared to others. Golub and Johnson (1994) found that in a sample of serious drug users, alcohol was not a prerequisite to marijuana use, especially for younger respondents. In their sample, a large proportion of drug users began their drug use with marijuana, and 15”/0 used cocaine or IV drugs without first using marijuana. In a study of Australian youths in which the sample was drawn from households rather than schools, Blaze-Temple and Lo (1992) reported that a substantial proportion (29%) of those who used ‘hard’ drugs (speed, LSD, cocaine, heroin) had never used marijuana. These findings suggest that those youths who are most at risk for becoming serious drug users may be least likely to follow the typical sequence of drug use initiation. Consequently, prevention campaigns which focus on preventing alcohol and marijuana use may not be effective for a large proportion of these high risk youth. Furthermore, those youths who bypass the gateway stage of ‘soft’ drug use (i.e. alcohol and marijuana), proceeding immediately to the use of ‘harder’ substances, may be at greater risk for developing a regular drug habit or addiction, or engaging in other types of problem behaviour. This study evaluated sequence of drug use in a sample of serious drug users from New York City (project DRIVE and FEMDRIVE; Goldstein et al., 1987: 1988). We compared the progression of drug use Deppendencr 45 (1997) 18% 196 in this sample with that in other samples from previous research. We hypothesized that this sample of drug users would not conform to the typical sequence of progression of drug use seen in other samples, that a substantial proportion would use marijuana prior to or in the absence of alcohol use, and that a substantial proportion would use other illicit drugs prior to or in the absence of marijuana use. As we had information on a greater number of illicit drugs than did Golub and Johnson (1994), we expected that the proportion using illicit drugs without prior use of marijuana would exceed their proportion of 15% who used cocaine or IV drugs without prior use of marijuana. If our samples do show more atypical sequencing than others, it may be due to some confounding factor that is associated with serious drug use. We examined the associations between atypical sequencing and several variables which have been associated with increased or decreased rates of drug use, including sex, ethnicity, child abuse victimization, birth cohort, criminality and age of first illicit drug use. Significant associations between sequencing and any of these variables would suggest a possible confounding effect. We then looked at the association between atypical sequencing and involvement in drug use within our samples, controlling for these potential confounding factors. We hypothesized that subgroups which have shown elevated rates of drug use would have higher rates of atypical sequencing. The Monitoring the Future study (Johnston et al., 1993) and other studies have found that Blacks report lower rates of use of illicit drugs. We predicted that Black subjects would have lower rates of atypical sequencing, compared to non-Blacks. Childhood physical and sexual abuse are associated with increased levels of drug use (Dembo et al., 1988; 1989; Bennett and Kemper, 1994). We predicted that subjects who were abused as children would show higher rates of atypical sequencing. We would also expect to find more atypical sequencing in birth cohorts that experienced elevated rates of illicit drug use. According to the National Household Survey on Drug Abuse (NIDA, 1988) and the Monitoring the Future study (Johnston et al., 1993) illicit drug use among high school students peaked around 1980. Since national epidemiologic data is not available for years prior to 1975, we do not have enough information to generate a firm hypothesis. However, we conducted an exploratory analysis and interpreted the results in light of available data. Previous research has shown that there is a significant association between substance use and other problem behaviours, such as delinquent, aggressive, or antisocial behaviour (Jessor and Jessor, 1977; Donovan and Jessor, 1985; Elliot et al., 1989). In their analysis of National Youth Survey data, Elliot et al. (1989) found a clear relationship between levels of drug use and delinquent behaviour. The most serious offenders had the M.E. Muckesy-Amici et al. /Drug and Alcohol highest rates of drug use, and nonoffenders the lowest. Conversely, polydrug users had the highest prevalence and offending rates of delinquent behaviour, followed by marijuana users, alcohol users and nonusers. Multiple illicit drug users accounted for highly disproportionate numbers of offenses. In addition, Elliot et al. reported evidence that it was early onset of illicit drug use that was associated with high risk for other forms of problem behaviour. We hypothesized that atypical sequencing would be associated with an earlier age of onset to illicit drug use, higher levels of drug involvement and increased criminal activity. 2. Methods 2.1. Subjects For this study, we analyzed data that had been collected from 152 men and 133 women in two ethnographic studies undertaken on the Lower East Side of New York City between 1984 and 1987. The studies were conducted to examine the drugs/violence nexus among adult drug users and distributors; the male sample was collected between November 1984 and April 1986 (project DRIVE; Goldstein et al., 1987), and the female sample was collected between April 1986 and May 1987 (project FEMDRIVE; Goldstein et al., 1988). Subjects were recruited from field contacts, through snowball sampling techniques (see Biernacki and Waldorf, 1981) and from a local methadone maintenance program. The goals of the research required the recruitment of subjects who were active in drug use or distribution at the time of the study. Respondents who were not active in these behaviours were excluded or dropped from the study. Interviewing took place in an ethnographic field station established solely for the purposes of these projects. The demographic characteristics of these samples are detailed elsewhere (Fendrich et al., 1992). 2.2. Procedure Details about the instruments used in these studies can be found in previously published papers (see Goldstein et al., 1987; Fendrich et al., 1992). Respondents in both studies were interviewed using similar semi-structured interview instruments. Upon recruitment to the study, all respondents were given a life history interview, which covered a wide range of issues including drug use history, participation in treatment programs, involvement in drug sales and distribution, criminal history and history of violence (victimization and perpetration). Life history interviews were completed in an average of three sessions for DRIVE men (Goldstein et al., 1987) and in an average of five sessions for FEMDRIVE women (Goldstein et al., 1988). Previous reports have discussed Dependence 45 (1997) 18% 196 187 methods used by the investigators to identify and eliminate dishonest respondents (see Fendrich et al., 1996). Additional analyses have examined the reliability of responses across and within interview phases (Fendrich et al., 1992, in press). The findings suggested that respondents showed a high level of consistency in terms of drug use disclosure, while reports of frequency and amounts of use showed less consistency. The subjects were asked about their lifetime and current use of 12 specific substances or types of substances: alcohol, marijuana, heroin, cocaine, street methadone, other opiates, barbiturates, amphetamines, tranquilizers, PCP, psychedelics (hallucinogens) and glue. They were also asked about any other drugs they used that were not covered in those categories. Thus, with the exception of tobacco, we have information on all the drugs the respondents ever used, to the extent that they were willing to disclose. Subjects who reported the use of either alcohol or marijuana, but did not report an age of first use were excluded from the analyses, leaving 120 men and 113 women. A profile of subject characteristics is presented in Table 1. Heroin and cocaine use were quite prevalent in both samples; 86% of the men and 89% of the women had used heroin and 98% of the men and all of the women had used cocaine. Most heroin and cocaine users were using at least three times a week during their most recent period of use. Drug use was extensive as well as intensive. DRIVE men reported using an average of 7.5 different substances in their lifetime, and reported current use of 3.5 substances; FEMDRIVE women reported using an average of seven different substances and current use of three substances. 2.2.1. Sequence of drug use All substances were ranked according to age of first use, allowing ties’. The information from ‘other’ drugs used was combined with information from the twelve specific substance types. Each other drug mentioned was classified by consulting the Physician’s Desk Reference, or based on the investigators’ knowledge of the drug’s effects*. The proportions of subjects who con- ’ For the purpose of making comparisons between the ranks of the various substances, those that were never used were coded as ‘98’. and missing values were coded as ‘97’. Thus, any substance with a missing age of first use (other than alcohol or marijuana) would be considered as if it had an onset later than any other substance that was used, but prior to any substance that had never been used. * The other drugs mentioned included inhalants, cough medicine, one hallucinogen (MDMA), one stimulant (Ritalin), three sedatives (Placidyl, Dalmane, Doriden), two anti-depressants with sedative effects (Elavil, Desyrel), one tranquilizer (Xanax), and quaaludes. The stimulants were grouped with amphetamines, the sedatives and antidepressants were grouped with barbiturates, inhalants were grouped with glue, and quaaludes were grouped with tranquilizers. Cough medicine, reported by one respondent, was not classified. 188 M.E. MackesJl-Amiri et al. 1 Drug and Alcohol formed to each of six possible sequences of drug use onset for alcohol, marijuana, and other illicit drugs were calculated. Concurrent use (e.g. of alcohol and marijuana) was treated as being in accordance with the hypothesized typical sequence of alcohol, marijuana, other illicit drugs (A-M-O). Thus, someone who used alcohol, marijuana and cocaine in their first year of drug use would be in the A-M-O category. We compared the findings from our samples of drug users with those from previous studies of conventional samples, and of serious or ‘hard’ drug users, by computing a 95% confidence interval around the proportion obtained in our combined samples, and observing whether the proportion observed in previous studies fell within the confidence limits. We did this for the proportion of subjects conforming to the A-M-O sequence, and for the proportion using marijuana prior to or concurrently with other illicit drugs. Table Profile Subject I of DRIVE and FEMDRIVE profile Mean age at interview Year at birth (range) Black (‘!(I) Hispanic (‘Xl) White/other (‘“;a) Single/divorced (‘Xl) Completed secondary school (“‘4) Shelter residence (‘Xl) Unemployed (“IL) Currently in drug treatment (‘1 r,) Currently in alcohol treatment (‘Xl) Average number of drugs ever used Average number of drugs currently used Ever used alcohol (‘Xl) Currently use alcohol (%I) Median frequency of alcohol use (days week) Ev,er used marijuana (‘!‘o) Currently use marijuana (‘%) Median frequency of marijuana use (days/week)” Ever used cocaine (‘!,;,I Currently use cocaine (%I) Median frequency of cocaine use (days/week) Ever used heroin (‘%I) Currently use heroin (‘!‘(I) Median frequency of heroin use (daysweek r’ Evrer deal drugs (‘X,) “ Typical frequency of use during samples DRIVE (N = 120) FEMDRIVE (N= 113) 31 1928 44 22 34 92 55 32 193441967 52 20 27 90 51 1966 51 86 38 40 93 40 8 3 7.5 7.0 3.5 2.9 93 74 I to 2 94 61 1 to 2 98 79 5 to 7 97 60 I to 2 98 80 3 to 4 100 76 3 to 4 86 SO 89 48 3 to 4 77 5 to 7 68 most recent period of use. Dependence 2.2.2. Correlates 45 (1997) 185-196 of drug use sequence We conducted a series of bivariate analyses (x2) to test the associations between typical versus atypical drug use sequence and sex, ethnicity, history of physical or sexual abuse, birth cohort, and measures of criminality, including ever committed a property crime (burglary, shoplifting, forgery or con games), ever committed a person crime (robbery/mugging, purse snatching or rape), and ever been in prison. Analyses were conducted for A-M-O versus any other sequence, use of alcohol before marijuana and use of marijuana before other illicit drugs. Due to small numbers in older cohorts, subjects born before 1943 were excluded from the analysis on birth cohort. Cohorts were defined as the five-year periods around 1945, 1950, 1955, 1960 and 1965. We conducted t-tests to look at the association between drug use sequence and measures of drug and criminal involvement, including age of first illicit drug use, age of first illicit drug use other than marijuana, number of drugs ever used regularlyj, number of drugs currently used4 and types of crimes ever committed. Drug use variables were coded for the longest period of use described’ by the subject for each substance reported. ‘Types of crimes ever committed’ was based on responses to life history interview questions about lifetime involvement in eleven different crimes5, and an additional category of ‘any other crime’. Subjects could report a maximum of twelve different crimes. For all bivariate analyses, including x2 and t-tests, P values were adjusted for multiple comparisons. Since there were twelve comparisons, the obtained P values were multiplied by twelve. Thus, an adjusted P value of 0.05 represents an obtained value of 0.05/12 or 0.004. Finally, we conducted logistic regression analyses, predicting atypical drug use sequence from background and criminal involvement variables, and from drug involvement variables controlling for background and criminal involvement variables. Analyses were conducted for the dependent variables A-M-O sequence versus all others (not A-M-O = 1) and marijuana-other illicit drug sequence (other before marijuana = 1). In the first step, the model included the background vari- ’ Regular use was defined as using three days a week or more. 4 Subjects were coded as currently using a substance if they explicitly stated that they were currently using, or if the last reported use was in the current year and they did not say that they were not using. Subjects who reported quitting a month or less ago were considered current users: subjects who ceased using more than a month ago were coded as not currently using, unless this period of non-use corresponded to their typical pattern of use (e.g. once every six months). ’ The crimes asked about were shoplifting, burglary, robbery/mugging, forgery, purse snatching, prostitution, pimping, drug dealing, other drug activity, con games and rape. FEMDRIVE subjects were also asked about assault, but this was not included in our analyses. M.E. Table Order 2 of use of alcohol, Order of drug marijuana use A-M-O A-O-M” M-A-O” M-O-Ah-’ O-A-M’.“ O-M-Ab’.C Mackes.v-Amiti and other Males illicit et al. /Drug and Alcohol Dependence 45 (1997) 185-196 189 drugs” (n = 120) Females (n = 113) Combined (n = 233) ‘%I N ‘%, N ‘%I N 36 14 8 16 15 12 43 17 Y 19 18 14 30 19 12 20 11 I 34 22 14 23 12 8 33 17 10 18 13 Y 77 39 23 42 30 22 ” Other illicit drugs include heroin. street methadone, psychedelics and glue/inhalants. b Marijuana use precedes alcohol use ’ Other illicit drug use precedes alcohol use. ’ Other illicit drug use precedes marijuana use. cocaine, other opiates, ables: sex, ethnicity, childhood abuse, birth cohort, and types of crimes ever committed. The ethnicity effect was set up as deviation contrasts, with Black versus all others and Hispanic versus all others. All other effects were set up as indicator variables. For birth cohort, the 1953357 cohort was chosen as the reference group. In the second step, number of drugs ever used regularly was added to the model and age of first other illicit drug use was added in the third step. 3. Results 3.1. Sequence of’ drug use Substantial proportions of subjects did not conform to the conditions described in previous studies. The proportions conforming to each of the six possible sequences of use of alcohol, marijuana, and other illicit drugs are shown in Table 2. The distributions were similar for males and females; females were slightly more likely to initiate with marijuana, while males were more likely to initiate with other illicit drugs. Although first alcohol use usually preceded, or was concurrent with first use of marijuana, 35”/0 of males and 40% of females in our samples used marijuana prior to any alcohol use (add rows 3, 4 and 6 in Table 2). In addition, about 40% of both males and females used other illicit drugs prior to any use of marijuana (add rows 2, 5 and 6). Less than half of the subjects (36% of males, 30% of females) followed the typical pathway described in previous studies, where alcohol use precedes marijuana use and marijuana use precedes the use of other illicit drugs. Table 3 shows previous studies that reported a proportion that we could use for comparison with our results. Each study reported either a proportion of subjects who conformed to a Guttman scale (either conventional or modified) in which alcohol preceded amphetamines/stimulants, barbiturates/sedatives, tranquilizers, PCP, marijuana and marijuana preceded other illicit drugs (A-M-O), or a proportion of subjects who used marijuana before using other illicit drugs (M < 0). Combining our two samples, 33% of the subjects conformed to the A-M-O sequence. The 95% confidence interval for this proportion is 27-39%; the lowest proportion reported in previous studies to follow the typical sequence was 75% (Andrews et al., 1991) and in most cases it was above 85%. None of the previous estimates fall within our confidence interval. In the combined sample, 61% of the subjects used marijuana prior to or concurrently with other illicit drugs. The 95% confidence interval for this proportion is 55567%. Blaze-Temple and Lo (1992) reported that 71% of ‘hard’ drug users in their sample used marijuana prior to other illicit drugs. Golub and Johnson (1994) reported that 85% of their sample used marijuana before other illicit drugs and the other three studies reported proportions exceeding 95%. None of these estimates fall within our confidence interval. 3.2. Correlates of drug use sequence The bivariate analyses of sex, ethnicity, .,childhood abuse and birth cohort are shown in Table 4. All P values were multiplied by 12 to adjust for multiple comparisons. There were no effects due to sex. The ethnicity effect was significant for the typical (A-M-O) versus atypical comparison (x f = r = 12.01, Bonferroni adjusted P < 0.05), and the marijuana before other illicit drugs comparison (x$= , = 15.21, Bonferroni adjusted P < 0.01). This was due mainly to Blacks being less likely to use other illicit drugs before marijuana compared to non-Blacks. Subjects who were abused as children were slightly more likely to use marijuana before alcohol, however, this was not a significant effect. There was a significant cohort effect only for marijuana before other illicit drugs (x$rZ4 = 18.52, Bonferroni adjusted P < 0.05). There is a small increase I90 Table 3 Percentage M.E. of subjects conforming Muckesy-Amiti to expected Study Guitman SC& (A-M-O) Andrews et al. (1991) Andrews et al. (1991) Blaze-Temple and Lo (1992) Brook et al. (1982) Donovan and Jessor (1983) Kandcl and Faust (1975) Kandel and Yamaguchi (1993) Yamaguchi and Kandel (198kd) Mackesy-Amiti, Fendrich and Goldstein 95% confidence interval Mar+xma h</ore other illicit drugs Blaze-Temple and Lo (1992) Donovan and Jessor (1983) Golub and Johnson (1994) Kandel (I 980) Y amaguchi and Kandel (1984b) Mackesy-Amiti. Fendrich and Goldstein 95% confidence interval -.--___~-__ “Smallest cigarettes reported or pills. percentage is given et al. /Drug sequence and Alcohol Dependence 45 (1997) 185-196 use Sample Observed 756 634 1093 663 9658 4847 1108 1325 90 75 85 90 92 90 93 86 33 (27-39) lo- 16 year olds recruited by advertisements lo-16 year olds: 1 year follow-up 13- 17 year olds in Perth households 9th and 10th grade students in public schools adolescents, grades 7-12 (national study) public high school students: 5/6 month follow-up 12th grade students in public and private schools former 10th and 11 th grade students at age 24-25 49 current illicit drug users age 13.--I7 in Perth households 3958 adolescents, grades lo- 12 (national study) 1003 drug abusers, inner city Manhattan (mean age 28) 5468 high school students: 5/6 month follow-up 1325 former 10th and 1 Ith grade students at age 24-25 where more than one result was reported. in using other illicit drugs before marijuana from the 1948 - 52 cohort to the 1953-57 cohort, followed by a sharp decline in this atypical sequence in the succeeding cohorts. x’-Tests on the dichotomous crime and prison variables (not shown) were not statistically significant. Stratified analyses revealed ethnicity effects that varied by sex (not shown). Hispanic women were more likely than either Black or White/Other women to follow an atypical sequence, and to use other illicit drugs before marijuana. Hispanic men were similar to White/Other men in the proportions of typical and atypical sequence. There were no other interactions by sex. The results of the t-tests on drug and criminal involvement variables are presented in Table 5. Two of the variables--age of first other illicit drug use (illicit drugs other than marijuana), and number of drugs ever used regularly---showed significant effects. Subjects who used other illicit drugs prior to marijuana use tended to begin their use of these drugs at an earlier age (14.0 years) than did those who used marijuana before using other illicit drugs (16.4 years; t,,, = 4.76, Bonferroni adjusted P < 0.01; adjusted for unequal variance)6. h This may appear tautological, however, it is not. While it seems most likely that persons who used other illicit drugs before marijuana began other illicit drug use at an earlier age than those who used marijuana first. this is not necessarily the case. They might have foregone marijuana use at the age when others were initiating marijuana use and taken up drug use at a later age, beginning with harder drugs about the same time others were ‘graduating’ from marijuana to harder drugs. If this were the case, the groups would differ on age of first illicit drug USC. but not on age of first other illicit drug use. In some cases the Guttman percentage” 71 99 85 96 97 61 (55 -67) scale included additional steps e.g. Subjects who followed an atypical progression of drug use onset (i.e. not A-M-O) tended to have used a greater number of drugs on a regular basis (t,:, = 3.26, Bonferroni adjusted P = 0.01; adjusted for unequal variance). There were no significant effects for number of drugs currently used, or number of crimes ever committed. The results of the logistic regression analyses are presented in Table 6 (A-M-O versus not A-M-O) and Table 7 (marijuana before other illicit drugs). The first model included the background variables: sex, ethnicity, birth cohort, childhood abuse, and types of crimes committed. The second model included the background variables, plus number of drugs ever used regularly. Age of first illicit drug use other than marijuana was added to these variables in the third model. For the dependent variable A-M-O sequence versus not A-M-O, ethnicity was the only background variable to reach significance in the first model (Wald = 6.9, P < 0.05); Blacks were less likely than non-Blacks to follow an atypical sequence (OR = 0.6; 95% CT 0.38 0.88). In the second model, number of drugs used regularly shows no significant association with drug use sequence, as shown by the Wald test and by the improvement in the model 1’. Age of first other illicit drug use (Model 3) was significantly associated with drug use sequence, as shown by the Wald test and the improvement in the model x2. Those who began other illicit drug use at an earlier age were more likely to follow an atypical sequence of drug use onset. For every one year increase in the age of first other illicit drug use, the odds of being in the atypical sequence category decrease by 0.9. M.E. Table 4 Subject background Subject background Sex Male Female Ethnicity White/other Hispanic Black Childhood Yes No by sequence et al. /Drug of drug onset: A-M-O” (‘X,) and Alcohol proportions Dependence and chi-square A<Mb 185- 196 191 tests N Not 120 113 64.2 69.9 0.87 12 49 73.6 81.6 12.01 * 112 56.3 117 116 73.5 60.3 4.56 44.4 30.2 5.07 41.0 37.1 0.38 26 67 65.4 70. I 5.10 23.1 31.3 6.45 46.2 46.3 18.52 * 45 54 28 77.8 64.8 53.6 x2 Not 45 (1997) (o/o) x2 Not 35.0 39.8 0.58 40.8 37.2 0.33 41.7 34.7 0.85 45.8 57.1 15.21 ** 35.7 M <O’ (X) x2 26.8 abuse Cohort 1943m 47 1948-m52 1953 57 1958862 1963367 ___~ * b ’ * variables Mackesy-Amiti Alcohol, marijuana. other illicit drugs. Alcohol before marijuana. Marijuana befort other illicit drugs. PcO.05, ** P~0.01 (corrected for multiple 48.9 40.7 42.9 55.6 29.6 10.7 comparisons). For the marijuana-other illicit drugs sequence, ethnicity (Wald = 7.9, P < 0.05) and cohort (Wald = 14.1, P < 0.01) were significant predictors in the first model. Again, Blacks were less likely than non-Blacks to follow the atypical sequence (other illicit drugs before marijuana); in addition, Hispanics were more likely than non-Hispanics to follow the atypical sequence. The significant contrasts for birth cohort were 1953-57 versus 1958-62 (OR =0.3; 95% CI 0.12-0.81) and 1953-57 versus 1963-67 (OR=O.l; 95% CI 0.040.33). The marijuana before other illicit drugs sequence was more prevalent in the later cohorts. In the second model, number of drugs used regularly again shows no significant association with drug use sequence when adjusting for the background variables. In Model 3, age of first other illicit drug use was again significantly associated with drug use sequence (OR = 0.8, 95% CI 0.70-0.86). For every one year increase in the age of first other illicit drug use, the odds of being in the atypical sequence category decrease by 0.8. 4. Discussion We examined the prevalence of drug sequencing patterns in two samples of serious drug users. The prevalence of sequencing in these samples diverged markedly from the prevalence observed in other studies. In particular, there was major divergence with respect to the prevalence of the alcohol-marijuana-other drug (A-MO) progression pattern. Whereas in previous studies examining sequencing, the vast majority of subjects followed the A-M-O pattern, in our samples, only about one third followed this pattern. In previous studies at least three quarters of all subjects initiated marijuana before initiating other substances, while in our study, only about three fifths of all subjects followed this pattern. In attempting to generalize results from our samples to other studies of similar issues, specific limitations need to be underscored. Our analyses were based on two ethnographic samples interviewed in distinct time periods (1986 and 1987) in a single location (New York City’s Lower East Side). The unique characteristics of this sample limit our capacity to make generalizations to other samples of drug users. Nevertheless, the pattern of findings raises a number of questions which may be useful in evaluating the generalizability of drug use sequencing hypotheses. What accounts for the discrepancies and divergence observed between findings from our study and other studies investigating drug use sequencing? Our samples and those employed in other studies differed in several ways. Our samples were characterized by extensive drug involvement; our subjects were generally older than subjects in other studies; our samples included relatively large proportions of Black and Hispanic persons; and socioeconomic indicators, including high school completion, shelter residence, and unemployment, suggest a high degree of poverty among our subjects. With respect to general levels of drug involvement, only two other studies selected a sample paralleling 192 M.E. Mackesy-Amiti et al. /Drug and Alcohol Dependence 45 (1997) 185-196 Table 5 Drug and criminal involvement by sequence of drug use onset T-tests Age of first illicit drug use” Age of first illicit drug use other than marijuana Number of drugs ever used regularly Number of drugs currently used Types of crimes ever committedb A-M-O Alcohol before marijuana Marijuana drugs before other illicit Typical n = 77 mean (S.D.) Atypical n = 156 Typical n = 146 Atypical n = 87 Typical n = 142 mean (SD.) mean (S.D.) mean (S.D.) mean (S.D) Atypical n = 91 mean (S.D.) 14.6 (2.6) 16.7 (3.1) 13.9 (3.7) 14.8 (3x)** 14.6 (3.6) 15.7 (4.0) 13.4 (2.9) 15.1 (3.3) 14.3 (2.7) 16.4 (3.0) 14.0 (4.2) 14.0 (4.2)** 3.5 (1.9) 4.5 (2.2)* 4.0 (2.2) 4.4 (2.1) 3.9 (2.1) 4.6 (2.3) 3.4 (1.8) 3.7 (2.1) 3.1 (1.8) 4.1 (2.2) 3.2 (1.8) 4.0 (2.3) 3.2 (1.7) 3.8 (2.1) 3.3 (1.7) 3.7 (2.1) 3.1 (1.8) 4.3 (2.3) “Illicit drugs are marijuana, cocaine, heroin, other opiates, street methadone, stimulants, sedatives, tranquilizers, PCP, inhalants and psychedelics. ‘Crimes are shoplifting, burglary, robbery/mugging, forgery, purse snatching, prostitution, pimping, drug dealing, other drug activity, con games, rape and any other crime. * PiO.05. ** P<O.Ol (corrected for multiple comparisons). those that we employed (Blaze-Temple and Lo, 1992; Golub and Johnson, 1994). However, Golub and Johnson included only cocaine and IV drugs as other illicit drugs in their analyses. It is interesting to note that the sequencing conformity rates for marijuana and other illicit drugs in the Blaze-Temple and Lo study paralleled the low rates that we observed in our samples. These parallels support the validity of our findings and suggest that there might be clear behavioral differences between occasional or experimental drug users and those who are more drug involved. Even within the context of our own serious drug using samples, higher rates of aberrant sequencing were associated with earlier initiation of illicit drugs other than marijuana, and greater lifetime drug involvement. We also found that ethnicity and birth cohort were significantly associated with drug use sequence. However, Blacks were the most prevalent ethnic group in our samples, and were the least likely to follow an atypical drug use sequence. Thus, the high prevalence of atypical sequencing cannot be explained by the large proportions of ethnic minorities in our samples. In addition, the association between sequencing and ethnicity may be a spurious effect due to the association between ethnicity and drug involvement (number of drugs used regularly). Blacks reported using fewer drugs than either Whites or Hispanics, and were least likely to follow an atypical sequence. As a result, when number of drugs used regularly was added to the logistic regression model, the ethnicity effect became non-significant. The cohort effects we found, on the other hand, may partially account for the discrepancies between the findings of this study and previous studies. Most of the previous studies used samples of high school students and we found that the youngest cohorts in our samples were most likely to exhibit the typical pattern of drug use sequence. These findings suggest that the sequencing of drugs is influenced by drug use norms which may be in effect during years of drug use initiation (see also, Golub and Johnson, 1994). We also note the low socioeconomic status of our subjects, as inferred by the high prevalence of homelessness and unemployment. The low rate of high school completion further suggests that the majority of the subjects probably were poor before they began using drugs. Our findings suggest the possibility that youths who grow up in poverty are less likely to follow the typical sequence of use onset found in general high school samples, and that this is related to early initiation of ‘hard’ drug use. Unfortunately, no data were collected from our samples regarding tobacco use. This may explain in part the high rate of initiation of substance use with marijuana. Many of those subjects who used marijuana prior to alcohol may have used tobacco before marijuana, in which case they would be consistent with a model in which marijuana use is preceded by the use of legal drugs (either alcohol or tobacco). However, this does not affect our findings with regard to the sequencing of marijuana and other illicit drugs. It should be underscored that one important variable that may affect empirical findings with respect to sequencing concerns the number of substances assessed in the interview. To our knowledge, our assessment was somewhat more comprehensive in its scope of illicit drug assessment than most others assessing drug use sequencing. In particular, we know of no other study which actually included inhalant use in the assessment of ‘other drug’ initiation. Clearly our inclusion of inhalants, substances characterized by relatively early age of onset (Smart, 1986), increased our likelihood of finding nonconformity to conventional sequencing. Nevertheless, we note that even if inhalants were ex- M.E. Mackesy-Amiti et al. /Drug and Alcohol Dependence 45 (1997) 185- 193 196 Table 6 Correlates of drug use sequence: logistic regression analysis predicting not A-M-O Subject background Sex Female” Male Ethnicity Other” Black Hispanic Childhood abuse No“ Yes Birth cohort 1943 -47 1948852 1953 -57” 195862 1963-67 Types of crimes ever done Model 1 Model 2 Model 3 Odds ratio (95% Cl) Odds ratio (95% CI) Odds ratio (95% CI) 1.0 1.0 0.8 (0.42L 1.57) 1.0 0.8 (0.41- 0.7 (0.34-1.33) 1.0 1.0 1.0 0.6 (0.38-0.88)* 0.6 (0.41LO.97) 0.7 (0.43-1.06) 1.7 (1.00-3.03) 1.8 (1.02-3.12) 1.8 (1.02. 3.26) 1.0 1.4 (0.75-2.60) 1.0 1.3 (0.72-2.51) 1.0 1.2 (0.6442.29) 0.5 (0.181.62) 0.5 (0.18-1.65) 0.8 (0.34L2.08) 0.8 (0.34-2.12) 1.1 (0.31-3.67) 1.1 (0.4332.88) 1.0 1.0 1.0 0.6 (0.25Sl.67) 0.7 (0.27-1.88) 0.5 (0.17T1.44) 0.6 1.1 1.1 (0.89-1.24) 1.o (0.86- 1.20) 1.1 (0.96-1.34) 1.1 (0.90-1.28) Number of drugs used regularly (0.19-1.71) Age of first ‘hard’ drug useb Model x2 improvement (df) 1.56) 0.8 (0.3lL2.28) 0.6 (0.20- 1.87) 0.9 (0.77TO.96)** 15.28 (9) 2.2 (1) 8.3 (l)** * Reference group. The ethnicity contrast was conducted as a deviation contrast. Odds ratios are for Black vs. all other and Hispanic vs. all other. All other contrasts are indicator variables. ‘Any illicit drug use other than marijuana. * P<O.O5, ** P<O.Ol eluded from the list of ‘other’ drugs, our sequencing patterns would have still diverged markedly from those found in previous studies7. Thus, our inclusion of inhalants as other drugs does not account for the contrast between the findings presented here and the findings presented in previous research, especially with respect to the A-M-O sequence divergence. Our findings, along with those presented by BlazeTemple and Lo (1992) suggest that conventional sequencing is not as prevalent in samples or subgroups characterized by high rates of serious drug use as it is in samples characterized largely by occasional or experimental use (see Andrews et al., 1991; Brook et al., ‘With inhalants excluded, 40% of the sample conformed to the A-M-O sequence (95% confidence interval 34 to 46%) and 69% used marijuana prior to or concurrently with other illicit drugs (95% confidence interval 63 to 75%). 1982; Kandel and Faust, 1975; Donovan and Jessor, 1983; Kandel and Yamaguchi, 1993). When examined in the context of other recently published data (see Miller, 1994), these findings underscore the limited generalizability of previous conclusions with respect to drug use sequences. Sequencing patterns may vary markedly, depending on the overall drug involvement of the sample under study. This hypothesized association between serious drug use and the lack of conventional sequencing has considerable prevention implications. The bulk of illicit drug consumption in the US is due to ‘chronic hardcore’ users. For example, chronic users comprise about 20% of the drug-using population, but consume about twothirds of the total amount of cocaine consumed in the country (ONDCP, 1995). Chronic, hardcore users experience more severe health consequences and are more likely to engage in criminal activity. For these reasons, the national drug control strategy identifies the reduction of chronic hardcore drug use through treatment as 194 M.E. Mackes.v-Amiti et al. /Drug and Alcohol Dependence 45 (1997) 185-196 Table I Correlates of drug use sequence: Logistic regression analysis predicting not marijuana before other illicit drug Subject backgound Model 1 Model 2 Model 3 Odds ratio (95% CI) Odds ratio (95% CI) Odds ratio (95% Cl) Sex Female” Male Ethnicity Other” Black Hispanic 1.0 1.0 I.0 1.4 (0.71-2.65) 1.4 (0.71-2.67) 1.1 (0.5442.15) 1.0 1.0 1.0 0.6 (0.39-0.89)* 1.8 (1.0333.14)* 0.6 (0.3880.91)* 1.8 (1.0333.15)* 0.7 (0.422 1.02) 1.9 (1.05.-3.34)* 1.0 1.0 (05~1.77) 1.0 1.0 (0.51-1.79) 0.7 (0.39.- 1.40) Birth cohort 1943-47 1948- 52 1953--57” 1958 -62 1963367 0.6 0.8 1.0 0.3 0.1 0.6 (0.20- 1.87) 0.8 (0.33-2.03) 1.0 0.3 (0.12-0.82)* 0.1 (0.04-0.34)** 1.9 (0.5446.44) 1.3 (0.50-3.35) 1.0 0.4 (0.14-0.99)* 0. I (0.04-0.37)** Types of crimes ever done 1.1 1.1 (0.90-1.24) 1.0 (0.85-1.18) 1.0 (0.84-1.17) 0.9 (0.76- 1.07) Childhood No” Yes abuse (0.20- 1.87) (0.3332.02) (0.12-0.81)* (0.0440.33)** Number of drugs used regularly Age of first ‘hard’ drug useb Model x2 improvement (df) 1.0 0.8 (0.70-0.86)*** 30.96 (9)*** 0.0 (I) 23.4 (l)*** ” Reference group. The ethnicity contrast was conducted as a deviation contrast. Odds ratios are for Black vs. all other and Hispanic vs. all other. All contrasts are indicator variables. ’ Any illicit drug use other than marijuana. * P<O.O5, ** P <O.Ol, *** P <o.oot. an important goal. By the same token, it is vital that prevention efforts reduce hardcore use as well as casual use. Prevention programs must reach high-risk adolescents as well as low-risk adolescents. Prevention strategies that focus on tobacco, alcohol and marijuana as gateway drugs, and presume that preventing or delaying their use will break the chain of events that leads to chronic, hardcore use, may be of limited value. If those who are more likely to be involved in serious drug abuse report minimal and later involvement with softer substances, messages targeting these gateway substances will not be effective as prevention. Drug abuse prevention messages based on the gateway model may be least effective for a segment of the population that potentially will abuse drugs the most. Evidence that mainstream approaches to drug use prevention may not reach youths at risk for serious drug involvement comes from a study of drug use among American Indian youth. Beauvais (1996) found that while there was a decline among American Indian youth in moderateinvolvement drug use from 1980 to 1992, there was no change in the rate of high-involvement drug use. The author concluded that prevention messages were reaching the more mainstream youth but were not reaching those who are more prone to serious drug use. Indeed, the economically deprived youth, living on the fringes of society, dropping out of school, often homeless, and at great risk for developing serious drug use problems, have not often been considered in the formulation of prevention strategies. Our work exemplifies the need for rethinking the impact of strategies formulated from research based on more M.E. Mackesy-Amiti et al. ,’ Drug and Alcohol conventional samples and underscores the need for further research on the developmental sequencing of drug use among serious drug users. Our findings, when viewed in the context of the unique characteristics of our samples, suggest a future direction for research. It would be useful to examine whether our findings hold up in epidemiological samples characterized largely by experimental use; that is, do extensively drug-involved individuals assessed in these samples show less conformity to conventional sequencing than other types of drug users? Secondary analyses of a range of data sets may provide evidence with respect to the generalizability of our findings. The findings also underscore the necessity for evaluating the relative effectiveness of prevention programs with low and high-risk adolescents (such as Johnson et al., 1990) and the utility of evaluating substance use beyond alcohol and marijuana, even among young adolescents. While prevention of alcohol and marijuana use, especially early use, is an important goal in its own right, as a strategy for preventing use of other illicit drugs it may be of limited utility. Those youth who are at greatest risk for illicit drug use may be least likely to follow the typical sequential pattern of progression from alcohol to marijuana to other illicit drugs. The variation in the prevalence of the typical pattern over time also suggests that the predominance of the A-M-O sequence may be a temporary phenomenon. Drug abuse prevention efforts need to focus more attention on the precursors of drug abuse, such as family dysfunction (Brook et al., 1986; Newcomb and Bentler, 1988), school failure (Elliot et al., 1989) behavior disorders (Zucker and Noll, 1982), economic and social deprivation etc. Early identification of, and intervention with youth who are affected by such problems is vital to drug abuse prevention efforts. Acknowledgements This research was supported in part by grants from the National Institute on Drug Abuse (R29DA07995 and F32DA05668) and by a grant from the University of Illinois at Chicago. 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