Portal de Periódicos da CAPES

Death of the ‘stepping‐stone’ hypothesis and the ‘gateway’ model? comments on Morral et al.

2002; Wiley; Volume: 97; Issue: 12 Linguagem: Inglês

10.1046/j.1360-0443.2002.00287.x

1360-0443

James C. Anthony,

Alcohol Consumption and Health Effects

AddictionVolume 97, Issue 12 p. 1505-1507 Free Access Death of the ‘stepping-stone’ hypothesis and the ‘gateway’ model? comments on Morral et al. JAMES C. ANTHONY, JAMES C. ANTHONY Professor, Mental Hygiene and Epidemiology Bloomberg School of Public Health The Johns Hopkins University 624 North Broadway Baltimore, MD 21205 USA E-mail: janthony@jhsph.eduSearch for more papers by this author JAMES C. ANTHONY, JAMES C. ANTHONY Professor, Mental Hygiene and Epidemiology Bloomberg School of Public Health The Johns Hopkins University 624 North Broadway Baltimore, MD 21205 USA E-mail: janthony@jhsph.eduSearch for more papers by this author First published: 11 December 2002 https://doi.org/10.1046/j.1360-0443.2002.00287.xCitations: 14AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Several years ago, Lynskey and colleagues advanced an idea that co-occurrence of alcohol, tobacco, and cannabis use by the mid-adolescent years can be explained by an underlying common factor, which might be something like an individual's propensity to come into contact with users of these drugs. Their study data, based upon rigorous follow-up of a birth cohort in Christchurch, New Zealand, helped to strengthen and confirm this interesting idea (Lynskey et al. 1998). Summarized elsewhere, recent twin studies have also invoked this idea, and have probed for common genetic susceptibility traits that might account for co-occurring drug use and drug dependence syndromes vs. traits that are more specific to one drug or another (Anthony & Helzer 2002). In the current issue of Addiction, Morral and colleagues revisit a similar idea in a slightly more complex approach (Morral et al. 2002). Their data are from cross-sectional slices of American samples, each slice encompassing the experience of many different birth cohorts. Focal points of their advanced statistical modeling are the timing and sequencing of legal and illegal drug use as manifest in the survey respondents’ reports about age at first experience with each drug. Building from Lynskey's work, Morral's research team offers new details within a mosaic of accumulating evidence about the ‘stepping-stone’ hypothesis and the descriptive ‘gateway’ model of youthful drug involvement. Results from their ‘time to event’ models are consistent with the idea that an underlying common factor is sufficient to account for the observed co-occurrence and sequencing of legal and illegal drug use. But is this the death of the stepping-stone hypothesis and the gateway model? and do these new details in the mosaic of evidence motivate a change in current policies about early onset tobacco, alcohol or marijuana use? In my judgement, probably not. These new details should prompt more detailed probing into the nature of the underlying common factors. With respect to the stepping-stone hypothesis, the just-cited work is enough to suggest that we should look back to the spring under the willows or towards the bank of the stream to discover what pushes us from one stepping stone of drug use to the next. and the gateway observations are incomplete without attention to the beginnings of the pathway that leads towards the modal gateway sequence, from most available to least available drugs. This is not the death of stepping-stone and gateway ideas: it is an elaboration. Perhaps the most important policy implication of the stepping-stone hypothesis and gateway model relates to the idea that we might be able to prevent occurrence of the more serious forms of youthful drug involvement by preventing or ameliorating the earlier forms (Wagner & Anthony 2002). Is there reason to reject this policy implication of the stepping-stone and gateway models when research teams led by Morral and others show us new evidence consistent with the idea that an underlying common factor can explain the co-occurrence and sequencing of legal and illegal drug use? I think not, reasoning from analogies learned in basic epidemiology and public health research. Consider, for example, the co-occurrence and temporal sequencing of chickenpox, shingles and the painful post-shingles neuralgia syndrome. As for a common cause, all of these clinical syndromes can be traced back to a single underlying common factor, which is an infection by varicella-zoster virus (VZV). At present, some 75% of us are personally and intimately familiar with the ‘pocks’ that occur after VZV reaches skin and causes lesions. Thereafter, VZV progresses to the nervous system for a latency period within dorsal root ganglia, during which there is transcription of its genome and expression of polypeptides. Reactivation of VZV within the host yields a separate disease in later life, commonly called shingles (herpes zoster), affecting some 20–30% of chickenpox cases. An estimated 50% of shingles cases seen at age 60 years develop an enduring painful syndrome of postherpetic neuralgia (PHN) (Dworkin et al. 1997, 2001; Dworkin & Portenoy 1996; Rentier et al. 1996; Sadzot-Delvaux et al. 1998). Clinically apparent chickenpox is strongly associated with clinically diagnosed shingles and PHN, an association that is completely due to the underlying common causal agent VZV. Even so, these facts about shared early causal pathways and the strong inter-relationships of the observed features do not imply identical pathogenesis, etiology and epidemiology. In the United States, attuned to the underlying common cause of chickenpox, shingles and PHN, we now seek to prevent VZV infection via an active ‘chickenpox immunization program’, with hope to gain near-term benefits in the form of reduced school absences for the children and reduced work absences for caretaking parents. There are some additional anticipated benefits in the form of reduced secondary consequences, including reduced shingles and PHN incidence rates some decades in the future. Nonetheless, expectation of these benefits has not stopped active lines of research on prevention and amelioration of shingles and PHN, which continue to impose health burdens on billions of world inhabitants, most with no feasible escape from VZV infection and chickenpox during childhood. In sum, after the discovery of VZV infection as the underlying common factor that explains co-occurrence and temporal sequencing of chickenpox, shingles and PHN, there was a public health policy change within the US. But the policy change was one that sought prevention of chickenpox, the first clinical step in the process, with sustained attention to the prevention and amelioration of shingles (the second clinically apparent step) and PHN (the third clinically apparent step). It follows that illumination of a common underlying vulnerability factor linking legal and illegal drug use might prompt a redoubling of efforts to prevent or ameliorate each step in the observable ‘stepping-stone’ or ‘gateway’ process that leads from alcohol and tobacco, to marijuana, and towards cocaine or other illegal drugs. Based on our public health experience with chickenpox, shingles and PHN, there is good reason to investigate the nature of the quite plausible underlying common factors that account for the co-occurrence and temporal sequencing of legal and illegal drug use. But if and when we discover the true nature of these underlying common factors, we probably should not abandon our efforts to delay or ameliorate non-essential drug-taking by the youngest members of our societies, even if we cannot prevent the non-essential drug-taking altogether. The stepping-stone hypothesis and gateway models are not dead. They are now illuminated with a new approach that draws upon advanced statistical models and high-speed computing power not available in their early days. This issue's contribution from Morral's group gives us more reason to complete fundamental research on the earliest causal antecedents of the stepping-stone and gateway sequences that lead towards serious drug involvement, clinical syndromes of drug dependence and the related hazards of drug-taking. Nevertheless, as in the case of applied VZV research to estimate the costs and benefits of the current mass immunization policy of the US Government, there is benefit in looking for answers to some policy questions, which take the underlying common factors as a given: • When we use the ‘cannabis shop’ approach, do we actually achieve a near-term delay in the time to a young person's first chance to try cocaine or heroin, and is there a reduced conditional probability of cocaine or heroin use, once the opportunity has occurred? Is there a long-term benefit in the form of later reduced occurrence of hazards attributable to non-essential cocaine or heroin use? In the process, do we run the risk of accumulating more cases of dependence on marijuana, or other hazards attributable to non-essential marijuana use? • Leaving aside the question of cannabis shops, what of simple decriminalization of simple possession and use of marijuana by adults age 18 years and older? Will the removal of criminal penalties for adults lead inevitably to increased occurrence of marijuana use and problems among minors and a shifting of the health burden in the direction of the most vulnerable segments of the population? • Based on evidence just reported by Gfroerer et al. (2002), the annual incidence of marijuana use among adolescents in the US in recent years is as high or higher than ever before, including the Haight-Ashbury and post-Vietnam years. Would the annual incidence of marijuana use go even higher if the US Government were to make a ‘guns–butter’ shift—shifting most of its ‘butter’ resources of marijuana prohibition towards the ‘guns’ necessities of 21st century anti-terrorism activities? Or, if there is no shift in these resources, will the new administration ride to glory on a descending limb of this marijuana epidemic curve, which is likely to be regressing upon the mean of a fluctuating trend? Let us hope that there are investigators who can and will answer these questions with definitive evidence of policy impact, using the work of Morral's research group as a stepping stone towards these accomplishments. References Anthony, J. C. & Helzer, J. E. (2002) Epidemiology of drug dependence. In: M. T. Tsuang & M. Tohen, eds. Textbook in Psychiatric Epidemiology, 2nd edn, pp. 479– 562 . New York: Wiley, Inc. Wiley Online LibraryWeb of Science®Google Scholar Dworkin, R. H., Carrington, D., Cunningham, A., Kost, R. G., Levin, M. J., McKendrick, M. W., Oxman, M. N., Rentier, B., Schmader, K. E., Tappeiner, G., Wassilew, S. W. & Whitley, R. J. (1997) Assessment of pain in herpes zoster: lessons learned from antiviral trials. Antiviral Research, 33, 73– 85.CrossrefCASPubMedWeb of Science®Google Scholar Dworkin, R. H., Nagasako, E. M., Johnson, R. W. & Griffin, D. R. (2001) Acute pain in herpes zoster: the famciclovir database project. Pain, 94, 113– 119.CrossrefCASPubMedWeb of Science®Google Scholar Dworkin, R. H. & Portenoy, R. K. (1996) Pain and its persistence in herpes zoster. Pain, 67, 241– 251.CrossrefCASPubMedWeb of Science®Google Scholar Gfroerer, J. C., Wu, L.-T. & Penne, M. A. (2002) Initiation of Marijuana Use: Trends, Patterns and Implications. Analytic Series A-17, DHHS publication no SMA 02–3711. Rockville, MD: Substance Abuse and Mental Health Services Administration, Office of Applied Studies. Google Scholar Lynskey, M. T., Fergusson, D. M. & Horwood, L. J. (1998) The origins of the correlations between tobacco, alcohol and cannabis use during adolescence. Journal of Child Psychology and Psychiatry, 39, 995– 1005. Wiley Online LibraryCASPubMedWeb of Science®Google Scholar Morral, A. R., McCaffrey, D. F. & Paddock, S. M. (2002) Reassessing the marijuana gateway effect. Addiction, 97, 1493– 1504 . Wiley Online LibraryPubMedWeb of Science®Google Scholar Rentier, B., Piette, J., Baudoux, L., Dubrus, S., Defechereux, P., Merville, M. P., Sadzot-Delvaux, C. & Schoonbroodt, S. (1996) Lessons to be learned from varicella-zoster virus. Veterinary Microbiology, 53, 55– 66.CrossrefCASPubMedWeb of Science®Google Scholar Sadzot-Delvaux, C., Arvin, A. M. & Rentier, B. (1998) Varicella-zoster virus IE63, a virion component expressed during latency and acute infection, elicits humoral and cellular immunity. Journal of Infection and Disease, 178 (Suppl. 1) , 43– 47. CrossrefCASPubMedWeb of Science®Google Scholar Wagner, F. A. & Anthony, J. C. (2002) Into the world of illegal drug use: exposure opportunity and other mechanisms linking the use of alcohol, tobacco, marijuana and cocaine. American Journal of Epidemiology, 15, 918– 925. CrossrefWeb of Science®Google Scholar Citing Literature Volume97, Issue12December 2002Pages 1505-1507 ReferencesRelatedInformation