Like alcohol and other drugs, most people who try cannabis use it only occasionally and lose interest it in by the time they reach their 20s.

Some people, however, find that they are in the habit of using cannabis regularly and begin to experience some problems associated with its use.

People who are more at risk of developing problems as a result of their cannabis use include those who:

• begin smoking cannabis before the age of 18 years
• have a history of other alcohol or drug problems
• have a history of mental health problems

To follow are brief descriptions of some of the problems that might be experienced by regular and/or heavy cannabis users. You might consider whether any of these are relevant to you if your doctor has raised his/her concerns with you.

Dependence

Historically, cannabis was not seen as a drug of dependence in the same way as heroin or alcohol, but cannabis dependence is now well recognised in the scientific community.

How would I know if I was dependent?

Dependence on cannabis means that the person needs to use cannabis just to feel ‘normal’. In order to be diagnosed as cannabis dependent, a person needs to experience at least three of the following in the one year:

• tolerance to the effects of cannabis (i.e. you need more cannabis to get the same effect)
• withdrawal symptoms when you stop using cannabis, such as irritability, poor appetite, trouble sleeping and feeling depressed
• using more cannabis than you intend to
• persistent desire to stop taking cannabis or to cut down and being unsuccessful at this
• spending lots of time obtaining, using or recovering from the use of cannabis
• giving up important activities in favour of using cannabis
• using cannabis even when you know it is causing you problems

How common is the problem?

It has been estimated that there are at least 200,000 people dependent on cannabis in Australia. About one in ten people who have tried cannabis at least once in their lifetime will become dependent on the drug. The more often you use cannabis, the more likely you are to become dependent. If someone uses cannabis every day, then they have a 50/50 chance of becoming dependent. Young people develop cannabis dependence more quickly than adults.

Why does it matter?

People who are dependent on cannabis are at a higher risk of suffering from the negative consequences of using the drug, such as short-term memory impairment, mental health problems and respiratory diseases (if cannabis is smoked).

Evidence is growing about the association between cannabis use and a range of psychotic symptoms and disorders such as feelings of paranoia and schizophrenia. Evidence suggests that cannabis may somehow trigger schizophrenia in those who are already at risk of developing the disorder. Those with a vulnerability to develop schizophrenia, such as having a family history of the illness, are strongly advised against using cannabis for this reason. The use of cannabis also makes the course of an episode of schizophrenia, longer, more severe and more difficult to treat. People with psychotic disorders such as schizophrenia and bipolar affective disorder are strongly advised to avoid cannabis use.

The relationship between cannabis use and the more common mental health problems of depression and anxiety is not as clear. Cannabis may seem to help ease depression before the effects of the drug wear off, however, smoking cannabis is more likely to make depression worse overall. Those who use cannabis have been shown to have higher levels of depression and depressive symptoms than those who do not use cannabis. Although results are mixed, there is a substantial amount of evidence to suggest that cannabis use, particularly frequent or heavy use, predicts depression later in life. Young women appear to be more likely to experience this effect.

Cannabis can lead to symptoms of anxiety in the short-term, but there is a lack of evidence pointing to cannabis as an important risk factor for chronic anxiety disorders.

Regular use and dependence also leads to problems with finances, conflict in relationships with family and friends, and employment problems. For young people in particular, studies are increasingly clear that cannabis use before the age of 18 years seriously disrupts educational achievement, which can have a negative impact throughout a person’s life.

Is there any treatment for cannabis dependence?

There are a number of treatment options available for cannabis-dependent people to cut down or quit. It has been found that even a single session with a counsellor can assist the cannabis- dependent person to bring about significant improvements in their level of use and well being. As yet, there are no effective pharmacological treatments to help reduce cannabis withdrawal symptoms or to block the effects of cannabis.