Addiction (1999) 94 (9), 1277± 1278

EDITORIAL

Cannabis dependence and withdrawal

As we reach into at least the third decade ofprevalent cannabis use of the modern era, is it justpossible that we are beginning to observe thematurationof discussion onsomecannabis-relatedissues? Cannabis remains a hot policy topic withstrong degrees of polarization of views on the risksand bene® ts of cannabis. Cannabis is now by farthe most commonly consumed illicit drug, with10± 30% of the population in Europe reporting everuse and signi® cant reports of chronicusage in somecountries.

This scale of usage and the gradual normaliza-tion of consumption in some populations allowsfor greater possibilities for more accurate epidemi-ological studies based partially on a readiness toself-report honestly on cannabis use and alsobecause the greater prevalence of use allows foreasier access to populations to study.

The growth in the size of the using populationand in particular the availability of populations ofchronic heavy users now opens the doors for moreprecise studies of the long-term impact of heavyusage. There are now some studies of the charac-teristics of long-term users (Swift et al., 1998) andthere appears to be a growing number of studiesof strategies for assisting in the cessation of can-nabis use.

Inability to cut down or stop cannabis use is areal phenomenon which has received surprisinglylimited attention until recently. This is presumablylinked to the debate on whether or not cannabisis addictive. This is a somewhat curious debate,given the animal literature on the subject. Toler-ance to cannabis, withdrawal from cannabis anddependence on cannabis is demonstrated clearlyin animals (Pertwe, 1991). Recent antagoniststudies further con® rm these withdrawal phenom-ena (Aceto et al., 1996). Withdrawal phenomenain humans have also been reported with much ofthe work being done in the 1970s. Jones (1983)has reviewed this topic comprehensively andreports that the signs of cannabis withdrawal havebeen relatively mild and are comparable to the

symptoms of withdrawal from short, low-dosetreatment with opioids or ethanol. These symp-toms may be dose-related. Irritability andincreased aggression may be associated with with-drawal in chronic cannabis users. Budney et al.,in this issue, report on a small sample of treatmentseekers who were experiencing withdrawal symp-toms. However, there are always problems differ-entiating withdrawal symptoms from other moodand anxiety symptoms in a population presentingto a treatment service. Swift et al. (1998) havereported on dependence in cohorts of long-termcannabis users. They reported limited withdrawalphenomena but argued that this may be relatedto the sample’ s ready access to cannabis on acontinuous basis. Large-scale population studiesreport signi® cant rates of cannabis dependence(Kessler et al., 1994; Farrell et al., 1998), partic-ularly in prison and homeless populations.

Does this now mean that there is no controversyaround the dependence liability of cannabis? Well,not exactly. We can now agree that many peoplemeetinternationallyagreedcriteria fordependencebut we are still not sure what it means and whatsigni® cance it has for the individual, for theclinician or on a public health level.

Dependence and the nature of dependence asdescribed originally was a dimensional descriptionof a provisional nature (Edwards & Gross, 1976).Overall there is a need for careful exploration ofthe meaning and nature of cannabis dependenceand its overall clinical utility and public healthsigni® cance. Such work is likely to be richlyproductive in an era with a growing population ofheavy cannabis users, some of whom seek help tostop their smoking habit. Cannabis as a habit ishere to stay.

MICHAEL FARRELL

Senior Lecturer and Consultant Psychiatrist,

National Addiction Centre, 4 Windsor Walk,

London SE5 8AF, UK

ISSN 0965± 2140 print/ISSN 1360-0443 online/99/091277± 02 Ó Society for the Study of Addiction to Alcohol and Other Drugs

Carfax Publishing, Taylor & Francis Limited

1278 Editorial

ReferencesBUDNEY, A., NOVY, P. & HUGHES, J. (1999) Marijuana

withdrawal among adults seeking treatment for mari-juana dependence, Addiction , 94, 1311± 1321.

EDWARDS, G. & GROSS, M. M. (1976) Alcohol depen-dence: provisional description of a clinical syn-drome, British Medical Journal, 1, 1058± 1061.

FARRELL, M., HOWES, S., TAYLOR, C. et al. (1998)Substance misuse and psychiatric comorbidity: anoverview of the OPCS national psychiatric morbiditysurvey, Addictive Behaviour, 23, 909± 918.

JONES, R. T. (1983) Cannabis withdrawal, in: FEHR, K.& KALANT, H. (Eds) Cannabis and Health Hazards,pp. 617± 689 (Toronto, Addiction Research Foun-dation).

KESSLER, R., MCGONAGLE, K., ZHAO, S. et al. (1994)Lifetime and 12 month prevalence of DSM-III-Rpsychiatric disorders in the United States: resultsfrom the National Comorbidity Survey, Archives ofGeneral Psychiatry, 51, 8± 19.

PERTWEE, R. (1991) Tolerance and dependence onpsychotropic cannabinoids, in: PRATT, J. A. (Ed.)The Biological Basis of Drug Tolerance and Dependence,pp. 232± 263 (San Diego, CA, Academic Press).

SWIFT, W., HALL, W., DIDCOTT, P. & REILLY, D.(1998) Patterns and correlates of cannabis depen-dence among long term users in an Australian ruralarea, Addiction, 93, 1149± 1160.