Fact File

Cannabis

by ABC Health and Wellbeing

Cannabis is the most commonly used illegal drug in Australia, but how does it affect your health?



[Image source: sxchange ]

Everybody knows that heroin is extremely bad for you. Most people would say that cocaine, ecstasy and LSD are too. But what about cannabis?

It's a fair question, because cannabis, or marijuana, is the most widely used illegal drug in Australia, especially by young people.

According to a survey conducted by Australian Institute of Health and Welfare, 35 per cent of the Australian population have used cannabis at least once. The health issues related to using cannabis tend to be overshadowed by the arguments about whether cannabis should be legal or not.

Those who argue it should be legalised argue that it's no more dangerous than alcohol. Those who don't think it should be legalised point to evidence that it can cause lung damage, brain damage and psychosis.

What is it?

Cannabis sativa. Cannabis is derived from the cannabis plant (Cannabis sativa). Those who use it know it by a variety of names, including marijuana, dope, grass, pot, weed and mull.

Cannabis sativa.

The predominant active chemical in cannabis is THC (delta-9-tetrahydrocannabinol); the flowering heads of the plant have higher THC levels than the leaves. The drug is usually ingested into the body by smoking the dried heads and leaves of the plant, or the resin (a gum secreted by the plant known as hashish or hash). Cannabis can also be added to food and eaten.

When under the influence of the drug people experience alterations of mood and perception. These can be mildly pleasant or disorientating and disturbing, depending on the dose and on the experience of the user.

Cannabis can:

increase perception of colour, sound, smell, taste and other sensations.

make users feel happy, relaxed, and less inhibited.

alter perception of time and space, often causing the user to think they are experiencing profound ideas or insights.

increase the appetite, leading to a craving for chocolate or junk food.

There are some physical effects too:

Cannabis decreases coordination and balance, making it dangerous to drive or operate machinery.

Other common immediate effects include increased heart rate, low blood pressure, faintness and reddened eyes.

There also can be a 'hangover' effect  drowsiness and poor coordination  lasting a couple of hours.

All these effects increase as the dose increases. If someone uses too much cannabis, or smokes a stronger batch than they're used to, they can have a bad time, becoming fearful, confused and paranoid. There isn't really anything that can be done except wait until the effects wear off, preferably in the company of another person.

Unlike heroin and cocaine, there have been no known deaths from an overdose of cannabis.

Is it safe?

Like alcohol and other drugs, occasional use of small quantities of cannabis is unlikely to cause any permanent health damage, except those associated with intoxication such as a motor vehicle accident.

But use it often, over a long period of time, and it's a different story. Here's how it can damage your health:

Cannabis damages your airways. Cannabis cigarettes have more tar than tobacco, and smokers often inhale deeply, holding the smoke in the lungs longer to increase the effects of the drug. Smokers have increased susceptibility to chest infections like bronchitis (which then take longer to clear up), and a greater chance of developing chronic bronchitis. If cannabis and tobacco are combined, the risk is greater still, and the user probably also has a greater risk of developing lung cancer than someone who only smokes tobacco.

It saps your energy. Some regular users report that they have less energy and motivation than people who don't use the drug, and their performance at work or school suffers accordingly. When these users stop smoking, their energy and motivation usually returns.

It impairs your mental performance. Regular cannabis use (using the drug daily, and perhaps more than weekly in younger users) diminishes a user's concentration, memory and the ability to learn. Even after stopping use, these effects can last for several months. Among those who begin use cannabis in their early teens the diminished cognitive function appears to be irreversible.

It can affect your sex hormones. For a few hours after use, cannabis can depress sperm production in men. It's also been associated with mild menstrual irregularities in women. Some long-term regular users report reduced sex drive.

It can affect your mental health. (see below).

How much do you have to use before you experience those negative effects?

There isn't a clear answer to this. For some users, such as those who are younger or have a history of serious mental illness, even weekly use may be too much.

It's not a good idea to use the drug at all if you're breastfeeding or pregnant. Women who smoke during pregnancy give birth to smaller, lighter babies than those who don't. The same is probably true for people with schizophrenia and heart disease  cannabis can worsen the symptoms of both.

Cannabis and mental illness

There's a lot of debate about whether cannabis use can cause psychotic illnesses like schizophrenia. This debate stems from the observation that people with schizophrenia are twice as likely to use cannabis compared to the general population. So does cannabis cause psychosis, or do people with psychosis use cannabis as a result of their illness?

The evidence seems to suggest that cannabis use is one of many factors that can combine to cause psychosis , but the mechanism by which this occurs is still far from clear. Other factors probably include your genetic predisposition to developing a psychotic illness. Research suggests that the younger you start using cannabis, the greater your risk of developing a psychotic illness, but that cannabis alone does not cause psychosis, and that you can still have a psychotic episode without having used cannabis.

A 2011 study found that cannabis use can hasten the onset of a psychotic illness by up to three years, and that delaying or stopping cannabis use could not just delay but even prevent some cases of psychosis. In fact, some researchers have suggested that stopping cannabis use could prevent about eight per cent of schizophrenia.

There is also debate about whether cannabis use can lead to other mental illnesses such as depression and anxiety, but the evidence is unclear. One study found a modest association between using cannabis as an adolescent and experiencing depression as an adult but there was no strong evidence to suggest that it is a cause of depression.

Dependence

Regular users of cannabis often develop a tolerance to the drug  in other words, they need to smoke more over time to get the same effect.

About one in 10 of those who have tried cannabis become dependent on it. This involves physical symptoms such as tolerance and withdrawal and the most common psychological symptoms of craving and inability to control use.

The drug subtly alters the user's brain chemistry: if they suddenly stop smoking it they experience withdrawal symptoms (sleep disturbance, irritability, anxiety and sweating) which can last about a week.

Treatment

Private and government-run drug clinics and centres offer rehabilitation and treatment programs using individual counselling, group therapy, medication and withdrawal programs or a combination of these approaches, depending on the clinic and the user.

Some of them aim to stop clients using the drug altogether. Others recognise this isn't always possible and focus on reducing the amount that people use.

Drug tests

Most routine drug screening tests can detect THC and its metabolites in blood, saliva and urine. It is stored in fatty tissue, so can be detected for quite a while after use in urine tests: three to five days after a one-off joint (cigarette), or in the case of a heavy user, up to 30 days after stopping the drug.

Medical use of cannabis

Although its use for this purpose is currently illegal is Australia, there are suggestions that cannabis could help relieve the symptoms of certain medical conditions such as multiple sclerosis, chronic pain, wasting due to HIV or cancer, and nausea caused by chemotherapy.

Even though the majority of people in Australia support a clinical trial of using cannabis to treat medical conditions and a change in legislation to allow the medical use of cannabis , there is a lack of in-depth clinical research into the therapeutical potential of cannabis. A survey of Australians using cannabis (illegally) for medical purposes (including chronic pain, depression, arthritis, persistent nausea and weight loss) reported that these users perceived cannabis to provide relief of their symptoms.

While the main stumbling block is its illegality, other issues surrounding the medical use of cannabis include the difficulty in obtaining a consistently reliable dose through smoking the natural product, the potential harms associated with smoking and side effects of smoking including the 'high' caused by THC and a dry mouth. There is also a lack of convincing evidence that it is superior to other available drugs.

There is a pharmaceutical version of cannabis called Sativex, a mouth spray containing THC and other cannabis extract called cannabidiol. Sativex is registered for use in several countries as a treatment for neuropathic pain in people with multiple sclerosis. Although it is not currently approved for use in Australia, a trial of the drug in cancer patients with pain is currently under way.

Reviewed by Professor Jan Copeland and Mr Paul Dillon from the National Cannabis Prevention and Information Centre.