Editor's note
Cannabis usage is often thought not to be a problem, and recent reclassifications of the drug in the UK and groups pushing for the legalization of marijuana encourage usage. This is unfortunate because cannabis usage is often problematic. A dependency syndrome can develop, and then withdrawal symptoms can complicate the efforts to stop using the substance. There are many medical and mental health problems that occur with chronic cannabis usage, and these include, most seriously, psychoses (see Chapter 26) problems with memory, motivation, psychomotor coordination, irritability, anxiety, and a host of other psychological difficulties. Pulmonary problems can occur because of the smoking of the substance. Yet, despite the problems inherent in chronic usage and despite the large number of people who probably have developed dependency on the substance, there remains very little in the way of effective interventions. There are not enough trials to even attempt a meta-analysis of interventions. There are really no good pharmacologic interventions. Cognitive-behavioural therapy, enhanced by contingency management techniques such as the use of vouchers, seems most effective. There is some evidence that the longer the length of exposure to these behavioural interventions, the greater the chance of success in being able to stop using the substance.
Introduction
Cannabis use remains the most prevalent form of illicit drug use in English speaking countries and the European Union, and its use is believed to be high in other countries where epidemiological data are not available (European Monitoring Centers for Drugs and Drug Addiction, 2003; Hall et al. 1999; SAMSHA, 2002).