International Journal of the Addictions

ISSN: 0020-773X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/isum19

Predicting Initial Use of Marijuana from Correlates of Marijuana Use: Assessment of Panel and CrossSectional Data 1969-1976 Wayne L. Lucas To cite this article: Wayne L. Lucas (1978) Predicting Initial Use of Marijuana from Correlates of Marijuana Use: Assessment of Panel and Cross-Sectional Data 1969-1976, International Journal of the Addictions, 13:7, 1035-1047, DOI: 10.3109/10826087809039324 To link to this article: http://dx.doi.org/10.3109/10826087809039324

Published online: 03 Jul 2009.

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The Jnternafional Journal of the Addictions, 13(7), 1035- 1047, 1978

Predicting Initial Use of Marijuana from Correlates of Marijuana Use: Assessment of Panel and Cross-Sectional Data 1969- 1976 Wayne L. Lucas, Ph.D Administration of Justice Department University of Missouri-Kansas City Kansas City, Missouri

Abstract Data from two college-student samples, collected through a panel design from 1969 to 1973 and a cross-sectional design in 1976, were analyzed to address three questions regarding initial marijuana use: ( 1 ) Which variables, believed associated with marijuana use, are most salient to predicting initial use of the drug? ( 2 ) Are variables salient to predicting initial use of marijuana consistent in predicting initial use over time? (3) Do a n y salient variables operate in combination to predict initial marijuana use'? Results indicated that salience of the variables to predicting initial marijuana use changed over time. Implications for drug-use prediction are offered based on the findings. 1035

Copyright @ 1978 by Marcel Dekker, Inc. All Rights Reserved. Neither this work nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher.

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This research addresses several crucial questions regarding the ability of selected factors to predict initial use of marijuana. Panel and crosssectional data were utilized to develop and compare models for predicting initial marijuana use. Past research has identified numerous variables which differentiate marijuana users from nonusers [e.g., age (Abelson et al., 1973, p. 632), sex (Hochman. 1972, p. 89). opportunity to use (Goodman, 1972, pp. 263-264)- attitude toward marijuana (Church et al., 1974, p. 321), friends' L I S of ~ marijuana (Lawrence and Velleman, 1974, p. 134)]. It is generally assumed that such factors indicate socialization processes (e.g., exposure to attitudes, values, and norms) at work within marijuana-using milieus which account for personal use of the drug (e.g., National Commission on Marijuana and Drug Abuse, 1972, p. 41). However, such explanations may not account for initiul use of marijuana. Various stages of drug use careers, with potentially different factors operating to produce or sustain use at the various stages, might have been represented in these data. To date, with few exceptions (e.g., Johnson, 1973; Jessor et al., 1973; Sadava and Forsyth, 1975a, 1975b; Lucas et al., 1975), research efforts have not addressed the problem of establishing predictive or explanatory variables (or i n i f i d marijuana use. The research here addresses three questions to variables associated with marijuana use: Which variables associated with marijuana use are most salient to predicting initial use of that drug? 2. Are the variables which demonstrate salience to predicting initial use of marijuana at one time consistent in their ability to predict initial use over time? 3. Do any of the variables salient to predicting initial use of marijuana interact or operate in combination to predict initial marijuana use? 1.

Results of analysis indicated the ability of factors related to marijuana use to account for first use of that drug.

METHODS Data from two research projects, both utilizing college student respondents but from different universities, were analyzed in this report. The longitudinal research employed a panel design collecting information

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from the same 103 individuals in 1969, 1971, and 1973. The cross-sectional research collected information from 108 individuals in 1976. The panel group subjects did not report marijuana use when originally interviewed in 1969, but the cross-sectional group included users as well as nonusers of marijuana. The two university populations sampled and research procedures followed were comparable for both data sets. [Details of methodological procedures are in Lucas et al. (1973, 1974, 1975), and Lucas (1976).] Variables selected for this study had been identified by past research as related to marijuana use. Further, differential association theory, which has found support from research on marijuana use (e.g., Kandel, 1974; Plant, 1975), was used as a guide for selecting variables for analyses. Variables chosen were viewed as potentially indicating participation in a social milieu comprised of reference others who use marijuana. These independent variables were (1) sex, (2) age, (3) educational attainment, (4) occupational status, (5) exposure to close marijuana-using friends, (6) opportunity to use marijuana, (7) expressed desire to try marijuana, (8) tolerant attitude toward marijuana use, (9) changes in attitude toward marijuana use, and (10) beliefs causing hesitancy to try marijuana. The dependent variable was the occurrence of marijuana use. Measurement of the variables provided assessment of respondent characteristics prior to first use of marijuana. [Detailed discussion of measurement is in Lucas (1976, pp. 40-53).]

FINDINGS During the 4-year interim of the panel project, 26 (25%) respondents reported experience with marijuana [I4 (147;) noted first use in 1971; 12 (12%) noted first use in 19731, while the remaining 77 participants (75%) abstained from use throughout the study. Sixty-five cross-sectional group respondents (60%) reported use of marijuana, and 43 (40%) subjects reported never using the drug. Salient Variables Predicting Initial Marijuana Use

Stepwise regression analyses determined which of the 10 independent variables were most salient to predicting initial use of marijuana. (All 10 variables were regressed on “marijuana use” when panel data were analyzed, but the “occupational status” variable was dropped from analysis of cross-sectional data in that all respondents here reported

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I038

LUCAS

"college student" as their occupation.) Data analyses indicated whether independent variables possessed at one point in time were predictive of initial marijuana use at a later point in time. Tables 1 and 2 present zeroorder correlations for all variabies entered in regression for both panel :ind cross-sectional data. TLtble 3 presents the salient predictors resulting from analyses using thc I969 to 1971 phase of the panel data. Two variables from 1969 here salient to predicting initial use of marijuana by 1971 (Fig. 1 ). "Tolerant attitudc toward marijuana use" was entered first in regression. explaining 1 T ' , ,of the variance in the dependent variable, followed by "opportunity to use marijuana" ( R 2 increased 7'1,,). Both variables were positively related to initial marijuana use and together explained over 18",, of the variance i n initial marijuana use by 1971. Stepwise regression using the 1971 to 1973 phase of the panel data indicated three variables from 1971 were salient to predicting initial mari.juana use by 1973 (see Table 4 and Fig. 2 ) . "Tolerant attitude toward mari.juana LISC" was entered first. explaining 14",,, of the variance in the dependent variable. followed by "educational attainment" ( R 2 increased 4'l0)and "opportunity to use marijuana" ( R 2increased 3",,). Each of these uriables was positively related to marijuana use and together explained over 21",, of the variance in initial marijuana use by 1973. Stepwise regression analysis of cross-sectional data identified five ~ariablesas salient to predicting initial use of marijuana (see Table 5 and Fig. 3). The sequence of variables entered in regression was ( I ) "age" ( R = 32",,). ( 2 ) "expressed desire to try marijuana" (R' increased 16",,j. (-3) "tolerant attitude toward marijuana use" (R' increased 4",,), ( 4 ) "exposure to close marijuana-using friends" (R' increased 2",,), and ( 5 ) "beliefs causing hesitancy to try marijuana" (R' increased 2",,). Three variables were positively related to marijuana use, indicating that expressed desire to try marijuana, tolerant attitude toward marijuana use. and having frequent contact with close marijuana-using friends predicted initial use of marijuana. Two variables were negatively related to marijuana use. indicating that the absence of beliefs causing hesitancy to try marijuana and being younger predicted initial use of marijuana. The five variables explained more than 55?;, of the variance in initial marijuam use. Consistency of Salient Variables to Predict Initial Marijuana Use

To determine whether the salient variables were consistent in their ability to predict marijuana use over time, comparisons were madc of

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"The bottom half of table presents values based on the 1969 to 1971 phase of panel data, and the top half of table presents values based on the 1971 to 1973 phase of panel data. bRefers to reported marijuana use in 1971 for the 1969 to 1971 phase of panel data and reported use in 1973 for the 1971-1973 phase of panel data.

Marujuana useb Sex Age Education Occupational status Friends using marijuana Opportunity Expressed desire rolerant attitude Change attitude Beliefs hesitancy

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Table 1 Correlation Values for All Variables Entered in Regression Analysis of Panel Data for Prediction of Marijuana Use"

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Marijuana use Sex Age Education Friends using marijuana Opportunity Expressed desire Tolerant attitude Change attitude Beliefs hesitancy

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Correlation Values for All Variables Entered in Regression Analysis of Cross-Sectional Data for Prediction of Marijuana Use

Table 2

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PREDICTING INITIAL USE OF MARIJUANA

Table 3 Results of Stepwise Regression for Prediction of Marijuana Use from Panel Data ( 1969 to 19711

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~~

Salient variables

Regression coefficient"

R2

Tolerant attitude Opportunity

,27509 ,26432

.11538 .18107

Fb (enter Change in R2 equation) -

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F' (remain at final step)

13.17 8.02

8.69 8.02

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"Standardized B presented. bFvalue to enter equation at .I0 significance level = 2.76. ' F value to remain in equation at .25 significance level = 1.34.

Table 4 Results of Stepwise Regression for Prediction of Marijuana Use from Panel Data (1971 to 7973)

Salient variables

Regression coefficient'

R2

Tolerant attitude Education Opportunity

,34564 ,20387 .I7321

.14038 .18524 ,21390

Change in R2

Fb (enter equation)

F' (remain at final step)

.04496 ,02867

14.20 4.75 3.10

12.35 4.49 3.10

"Standardized B presented. bF value to enter equation at .lo significance level = 2.76. 'F value to remain in equation at .25 significance level = 1.34.

Tolerant attitude

Marijuana

Fig. 1. Model depicting salient variables for prediction of marijuana use from panel data (1969 to 1971).

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Marijuana use

I'ig. 2. Model depicting salient variahlca for prediction of marijuana use from panel data l

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hesitancy Fig. 3. Model depicting salient variables for prediction of marijuana use from crosssectional data.

the panel sample (i.e., “tolerant attitude” entered first in stepwise regression of panel data, but entered third from cross-sectional data). The differences observed when comparing these models suggests that the salient variables lacked consistency in their ability to predict initial use of marijuana over time. Interaction or Combined Effects of Salient Variables in Predicting Initial Marijuana Use

To determine whether salient variables from the models operated in combination to predict initial marijuana use, results from the models with and without interaction terms were compared. (Procedures used are outlined in Kerlinger and Pedhazur, 1973, pp. 159-160, 251-259.) The impact of interactions between Extrinsic and Intrinsic salient variables on initial marijuana use were assessed. Extrinsic factors are those external to an individual that are part of the social situation or milieu (e.g., exposure

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t o close marijuana-using friends. opportunity to use marijuana). Intrinsic [actors operate within the individual to produce or maintain abstention

lrom marijuana use (e.g.. expressed desire to try marijuana, tolerant :ittittide toward marijuana use. beliefs causing hesitancy to try marijuana). Results of tests for interaction effects are presented in Table 6. The addition of variables accounting for "opportunity,tolerant attitude" intcractions did not significantly explain more variance in initial mari.jum;i use among panel respondents in either the 1969 to 1971 model (R' increaxc = 0.02. I;'= 2.67). or the 1971 to 1973 model (R' increase = 0,004. I.' = 0.41 5). From the cross-sectional data, separate additions of \ ariables to thc model accounting for interactions of "friends using tn;ii-i.juana,expressed desire" (R' increase = 0.004. F = 0.975). "friends using riiarijuana'tolerant attitude" (R' increase = 0.00002. F = 0.005). and "friends using marijuana,beliefs hesitancy" ( R 2 increase = 0.00001. 1E' = 0.005) in no case significantly explained more variance in initial marijuana use. Thus none of the salient variables from panel or crosssectional data operated in combination to predict marijuana use.

Table 6 Results of Tests for Interaction Effects of Salient Extrinsic and Intrinsic Variables from the Models Models compared 1969 to 1971 model with opportunity/tolerant attitude interaction 1971 to 1973 model with opportunity/tolerant attitude interaction Cross-sectional model with friends using marijuana/expressed desire interaction Cross-sectional model with friends using marijuana/tolerant attitude interaction Cross-sectional model with friends using marijuana/beliefs hesitancy interact ion

Degrees of freedom

Fa

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1 and 99

2.67

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1 and 84

0.415

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,00427

1 and 101

0.975

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0.005

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1 and 101

0.005

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Change in R2

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=

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DISCUSSION The findings here indicated that factors associated with marijuana users or using groups were not necessarily predictive of first use of the drug. Of 10 variables assessed, no more than three predicted initial marijuana use among panel respondents, and five variables were salient to first use among cross-sectional respondents. This suggests that factors explaining why someone begins use of marijuana may differ from factors explaining why someone sustains use of the drug. Further, factors influencing first use of marijuana appear to operate in a dynamic rather than static relationship, indicated by the changing salience of the variables to initial marijuana use over time. Results from this project suggest several implications for marijuanause treatment and prevention programs. First, “treatment” and “prevention” seem to encompass two different realms. While all 10 of the variables initially entered in analysis may be appropriate for treatment programs (i.e., all associated with marijuana users or using groups), only those salient to first use of marijuana may be appropriate for prevention programs. Second, the fact that the salient variables were not consistent in their ability to predict initial marijuana use over time suggests that prevention programs should be alert to possible changes in the saliency of factors implemented in these programs. Prevention programs have an obligation to keep abreast of such changes and be prepared to alter programs according to the changes observed over time. Third, results from the most recent data (i.e., 1976) suggest that prevention programs would be most successful if they substantively ( 1 ) focused on younger individuals (i.e., adolescents), attempting to (2) arrest desires to try marijuana, (3) foster less tolerant attitudes toward use, (4) discourage friendships with users, and ( 5 ) foster beliefs which would make individuals hesitate to try the drug, Although this research identifies such salient factors, it cannot suggest viable programs for directly dealing with these factors if, indeed, such should exist. Manipulation of these factors raises serious ethical and practical issues for marijuana-use prevention programs. Ethically, attempts to directly manipulate the attitudes, beliefs, and social milieu of youth may not constitute “proper” activity for prevention programs. Further, in light of increasing social tolerance toward marijuana use, attempts to foster negative beliefs about marijuana may result in alientation of youth from

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thcse programs. Practically. attempts to directly manipulate the factors hcre on an individual case basis would be next to impossible. The number of'cxes today where, for example, a desire to try the drug exists, or friends \v ho use marijuana are present, would be astronomical. requiring mammoth prevention programs. Additionally, the 1976 data analysis indicated that "age" accounted for nearly one-third the variance in initial marijuana use, suggesting that the most effective prevention program would be one which made an individual older! Prevention programs have an obligation to consider the etliical and practical issues raised, and devise specific operations which will result in cffective programs. Because the salient variables identified cannot be directly manipulated, it appears that programs should focus on manipulable factors which may indirectly efTect initial marijuana use. Prevention programs might do well to work with community agencies in developing legitimate opportunities for youth ( e g , jobs, meaningful educational experience, recreational opportunities), which would operate to make drug use less desirable in relation to other available activities. Cooperation from schools, businesses, and community service groups would be essential in creating such opportunities. While several factors related to first use of marijuana were identified here. still large amounts of variance in initial use were not explained. Future research to determine other factors salient to first use of the drug is needed, particularly factors which might lend themselves to direct manipulation. Additionally. research employing larger samples than were utilized here. and focusing on adolescent populations, seems in order. Results from such research will help identify variables which consistently predict initial marijuana use. and suggest causal relationships in the process 01' becoming a marijuana user. REFERENCES ,AHELSON. H.. COHEN. R.. SCHRAYER. D., and RAPPEPORT, M. Drug experience. altitudes and related behavior among adolescents and adults. In National Commission on Marihuana and Drug Abuse. Appeiidi.~,Dr.11~Use j n Anier.ir.u: P i d ~ / i v i iill Prrc ~ i w r r w . L ~ ~ J I L I I IJ :I ~PuiiwiiJ , und C ' ~ ~ r r . ~ 1 ~ 4 1 r m of c e . cDrug C.W.Washington. D.C.: C.S. Govcrnment Printing Office. 1973. pp. 489-867. C'HURCH. M.A.. TRUSS. C.V., and MARTINO, E.R. Trends i n psychoactike drug use a n d in attitudcs toward inarijiiana ar a large metropolitan universitj J . C ~ ~ I I . W / . I'\.I.c/I(I~. 21 ( M a y j: 228 -23 I , 1974. C;OOI>MAN. J . K . Preventing the causes of drug abuse. J . Drug E h c . Z(Septemberj: 263 268. 1973.

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HOCHMAN, J.S. Marijuana and Social Evolution. Englewood ClIffs, New Jersey: PrenticeHall, 1972. JESSOR, R., JESSOR, S.I., and FINNEY, J. A social psychology of marijuana use: Longitudinal studies of high school and college youth. J . Pers. Soc. Psychol. 26(April): 1-15, 1973. JOHNSON, B.D. Marihuanu Users and Drug Subcultures. New York: Wiley, 1973. KANDEL, D. Inter- and intragenerational influences on adolescent marijuana use. J . Soc. Issues 30(2) : 107-135, 1974. KERLINGER, F.N., and PEDHAZUR, E.J. Multiple Regression in Behavioral Research. New York: Holt, Rinehart and Winston, 1973. LAWRENCE. T.S., and VELLEMAN, J.D. Correlates of student drug use in a suburban high school. Psj>chiatrj37(May): 129-136, 1974. LUCAS, W.L. Initiation to Mnr~juanaUse: Analysis of Panel Data in a Predictive Model Framework. Unpublished Doctoral Dissertation. Iowa State University, 1976. LUCAS, W.L., GRUPP, S.E., and SCHMITT, R.L. Predicting who will turn on. In S. E. Grupp (ed.) The Marihuana Muddle. Lexington, Massachusetts: Heath, 1973. LUCAS W.L., GRUPP, S.E., and SCHMITT, R.L. Longitudinal research and marijuana smoking: A successful approach. Criminology 12(November): 3 15-327, 1974. LUCAS, W.L., GRUPP, S.E., and SCHMITT, R.L. Predicting who will turn on : A fouryear follow-up. Int. J . Acidic[. lO(2): 305-326, 1975. NATIONAL COMMISSION O N MARIHUANA AND D R U G ABUSE. .Marihuana: A Signal of Misunderstanding. First Report of’the National Conmission on Marihuana arid Drug Abuse. Washington, D.C. U S . Government Printing Office, 1972. PLANT. M.A. Drugtakers in an English Town. London: Tavistock, 1975. SADAVA. S.W., and FORSYTH. R . Person- Environnient Interaction and College Student Drug Use: A Multiiwiarr Lungiluflkal Sruc/v. St. Catherines. Ontario: Brock University, unpublished, 1975a. SADAVA. S.W., and FORSYTH, R. Turning On, Turning Off and Relupse: Social Psjchological Determinants of’Starus Change in Cannabis Use. St. Catherines. Ontario: Brock University, unpublished, 1975b.

Predicting initial use of marijuana from correlates of marijuana use: assessment of panel and cross-sectional data 1969--1976.

International Journal of the Addictions ISSN: 0020-773X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/isum19 Predicting Initial...
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