Although the number of treatment options and the effectiveness of treatments has gradually increased over the past two decades, there has been a traditional lack of effective clinical interventions for cannabis users. This is possibly because cannabis has been viewed as non-dependence forming and, relative to some other drugs of abuse, less harmful. However, there appears to be a big demand for an effective treatment service for cannabis users who would like help in quitting. Anecdotal evidence from cannabis users seeking help suggests that they are discouraged from attending drug treatment agencies and units where preference is given to users of so-called harder' drugs. Some cannabis users have even reported attempting to join 12-step programs such as Alcoholics Anonymous or Narcotics Anonymous, but are often disappointed to find that these organisations are not oriented to meet their specific needs.
The need for appropriate clinical interventions for managing cannabis problems has been promoted by several recent lines of research.

Firstly, there has been increasing recognition of the harms associated with long-term, heavy cannabis use. As well as clear evidence for certain medical and psychological problems, there is also evidence that long-term users have a substantial risk of developing symptoms of cannabis dependence (Hall, Solowij & Lemon, 1994).

The major criteria for diagnosing cannabis dependence include the development of tolerance, evidence of withdrawal symptoms upon cessation of use, cannabis taken in larger amounts or for a longer period of time than intended, unsuccessful efforts to cut down, much time spent using or recovering from its effects, neglect of important social, occupational or recreational activities, and continued use despite knowledge of the onset of medical or psychological harms.

While different treatment options for cannabis cessation have been tried over the past two decades, there has been very little systematic research towards developing a `best practice' model for treating cannabis dependence. To put it simply, we still do not know the most effective and efficient way to provide treatment for cannabis users who want help to quit.

There has been recent promising research on the use of cognitive- behavioural therapeutic techniques in the treatment of cannabis dependence. Cognitive behaviour therapy (CBT) has been demonstrated to have efficacy that is at least as good, if not more effective, that comparable treatment modalities (Andrews, 1991; Barlow & Hofmann, 1997). This includes treatment for abuse and dependence of alcohol and other drugs (Mattick & Jarvis, 1993; Project MATCH Research Group, 1997). The major aim of CBT is to assist clients to manage or overcome the primary problem, i.e. repeated drug use, by developing and using specific skills or techniques. Cognitive techniques assist clients in changing certain thought processes that underlie drug dependence such as control of urges and cravings, improving confidence in resisting drug use, challenging outcome expectancies or beliefs regarding the perceived benefits of drug use, and learning control over irrational or intrusive thoughts that trigger negative emotions and promote drug use. Behavioural techniques generally involve self-monitoring of drug use behaviour and its antecedent mood and craving states, developing alternative activities to drug use, and the adoption of effective coping strategies that can be used when threatened by a high risk or potential relapse situation. Together, cognitive and behavioural techniques provide a powerful `package' for assisting clients to quit drug use, as well as maintaining abstinence in the longer term by preventing relapse (Jarvis, Tebbutt & Mattick, 1995; Marlatt & Gordon, 1985).

Recent research in the United States by Roffman and Stephens has provided the first demonstrations of the effectiveness of CBT in helping long-term users to quit. They used a group-based CBT approach and compared a longer (14 weekly sessions) intervention with a brief (2 sessions) intervention. Both interventions were effective in assisting clients to reduce frequency of smoking or to abstain from cannabis, compared with a no-treatment control group over a 12-month period.

The present research being carried out at NDARC in Sydney was developed in order to meet the demands of the increasing need for effective treatment for cannabis dependence in an Australian context. Our challenge is to develop an intervention that is brief and effective, as well as being appealing to prospective clients. CBT provides promise on all of these counts: it is by nature a briefer form of intervention, and is consistently shown to be of at least equal efficacy to other effective treatment options.

Therefore, we have developed two CBT programs: one of six sessions, and a brief intervention of just one session. There is now a good deal of evidence from the alcohol and tobacco treatment fields which indicates that brief interventions of one session can have considerable impact on an individual's substance use, and compare favourably with multiple sessions interventions (e.g. Heather, 1989).

The present study, which is still in progress, is a randomised controlled trial of the two brief CBT interventions. The purpose of the study is to:

· demonstrate the effectiveness of CBT treatment in helping long-term users to quite; and

· compare the effectiveness of the six-session CBT program against the one-session intervention.

The trial involves allocating clients on a random basis to one of the two CBT treatments, or to a control group in which treatment is delayed until after a six-month follow-up interview.

The success of the treatments will be determined by smoking status six months after finishing treatment, as well as by reductions in:

· level of cannabis use (self-report and urinalysis);

· severity of dependence;

· global cannabis-related problems; and

· adverse psychological symptoms.

Both CBT interventions deal with the person's thoughts, feelings and behaviours that are connected with heavy cannabis smoking. The therapy focuses on the context in which the individual's smoking typically occurs and allows clients to develop skills or strategies for changing the problematic thoughts and behaviours that perpetuate cannabis dependence. These cognitive- behavioural techniques are designed to enable permanent change in the individual's use of cannabis.

At the conclusion of the program, clients are given a booklet which outlines the general details of the session and provides a resource for future reference. This was intended to ensure that clients continued to work on their quit strategy after finishing therapy. (This booklet will be available from NDARC in the near future, as a self-help guide for individuals wishing to quit smoking cannabis.)

The present study is still in progress and so final results are not yet available. At the present stage, over 220 clients have been assessed and either provided with treatment or placed on the waiting list. Follow-up interviews are currently taking place for those clients who have reached the six month time lapse since concluding treatment.

Clients on the waiting list who have completed the follow-up interview are being invited to commence the program and are given the option of receiving either one or six sessions of CBT. Observing clients' preferences for a brief intervention or longer program will also provide us with more information about the attractiveness of the interventions on offer. Ultimately, we hope to be able to provide additional treatment options, with proven effectiveness, for cannabis users who want to quit. Furthermore, users should be able to know which of the two treatment options will be more suitable for clients based on their smoking pattern and readiness to commence quitting.