Cannabis is a drug that can be derived from one of three species of cannabis plants (Cannabis sativa, Cannabis indica, and Cannabis ruderalis). Cannabis is also known as marijuana, grass, pot, dope, Mary Jane, hooch, weed, hash, joints, brew, reefers, cones, smoke, mull, buddha, ganga, hydro, yarndi, heads and green.

There are three main forms of illicit cannabis: the dried leaves and flowers (heads), hashish, and hash oil (see FAQ ‘Are there different forms of cannabis?’). All three forms of cannabis are associated with a variety of physical and mental health problems. The use of any form of cannabis can also lead to social and financial difficulties, poorer educational outcomes, and the breakdown of relationships with family and friends.

Although cannabis can be grown in almost any climate, it thrives in warm areas and is increasingly cultivated by means of indoor hydroponic technology. There are more than 500 chemical compounds in cannabis, but the main psychoactive component is delta-9-tetrahydrocannabinol (THC). When cannabis is used, THC is the main active chemical constituent absorbed into the bloodstream, activating receptors in the brain to produce the associated “high”.

Cannabis is listed as a narcotic drug under the Narcotic Drugs Act 1967. Consequently, it is tightly controlled in Australia. The cultivation, production, manufacture, import, export, distribution, trade, possession, use and supply of cannabis and cannabis derived products are regulated by a number of Commonwealth, State and Territory laws. For more information about cannabis-related laws, see Cannabis & Crime.

Most people who use cannabis illicitly do so to experience a sense of mild euphoria and relaxation, often referred to as a ‘high’. Cannabis causes changes in the user's mood and also affects how they think and perceive the environment, e.g., everyday activities such as watching television and listening to music can be more intense.

Cannabis in the form of dried leaves or flowers (heads) is usually smoked in hand-rolled cigarettes (known as ‘joints’), or in pipes or special water pipes (‘bongs’). The dried leaves and heads can also be mixed with tobacco before being smoked.

Hashish is usually crumbled and smoked in a pipe or bong. It can also be mixed with tobacco, cannabis leaf, or cannabis head before being smoked.

Hash oil is usually applied in small quantities to cannabis leaf, head, or tobacco cigarettes and smoked.  It can also be heated and the vapour inhaled.

All three forms of cannabis can also be added to food and eaten.

There are three main forms of illicit cannabis: the dried leaves and flowers (heads) of the cannabis plant; hashish; and hash oil.  Hashish is made from the resin (a secreted gum) of the cannabis plant. It is extracted from the cannabis plant, dried and pressed into small blocks. Hash oil is a thick oil that is distilled from the cannabis plant or hashish. The dried leaf of the cannabis plant is the least potent form of cannabis, while hash oil is the most potent form.

Synthetic cannabinoids are manufactured chemicals that produce an effect similar to the psychoactive component of cannabis (delta-9-tetrahydrocannabinol or THC). These chemicals are combined with plant material to produce a synthetic form of cannabis.

In recent years, a wide variety of synthetic cannabinoid products have been made available as smoking mixtures that are sold on the Internet and in various specialised shops. These products are usually sold in foil sachets, typically containing 1-3 grams of dried plant matter to which chemicals that mimic the effects of THC have been added. A number of plant-based ingredients are often listed on the packaging, but scientific testing has found that many of these are not actually present.

In order to minimise associated harms, synthetic cannabinoids have been included as a scheduled prohibited substance (Schedule 9) under the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP). This means that the use of synthetic cannabinoids is illegal.

The immediate short-term effects of illicit cannabis use may include:

• a feeling of well-being
• talkativeness
• drowsiness
• loss of inhibitions
• decreased nausea
• increased appetite
• loss of coordination
• bloodshot eyes
• dryness of the eyes, mouth and throat
• anxiety and paranoia.

There is limited research on the long-term effects of illicit cannabis use. Available evidence indicates that probable adverse effects include:

• memory problems
• impaired learning abilities
• decreased motivation
• poorer concentration.

Smoking cannabis (either alone or in combination with tobacco) may additionally give rise to respiratory problems, including coughing and phlegm, chronic bronchitis, and cancer. There is also concern about links between cannabis use and mental health disorders, and the risk of dependence.

Illicit cannabis use can result in a range of adverse physical and mental health outcomes.

Physical health

Over the long-term, inhaling cannabis smoke is likely to result in damage to the respiratory system and may cause cancer. This damage has been shown to be present even in the absence of tobacco smoke, while harms appear to be additive for individuals who smoke both tobacco and cannabis.

Mental health

Cannabis use has been linked to a range of mental health conditions including:

• panic attacks
• depression and anxiety
• psychotic episodes
• schizophrenia
• dependence.

Not everyone who uses cannabis develops mental health issues. However, for some people cannabis can contribute to the development of mental health symptoms or make an existing mental health condition worse. Cannabis related mental health problems can arise at any stage of cannabis use. 

Illicit cannabis appears to be more potent now than it was in previous years. The potency of cannabis is determined by several factors including:

• the level of delta-9-tetrahydrocannabinol (THC - the main psychoactive chemical in cannabis)
• the way the cannabis plant is grown (e.g., hydroponics)
• the part of the cannabis plant used (e.g., head vs. leaf)
• the way cannabis is prepared for use (e.g., pipes/bongs vs. joints).

If you are worried about your own or somebody else’s cannabis use, contact the Alcohol and Drug Information Service (ADIS). The Alcohol and Drug Information Centres are state and territory-based services that offer information, advice, referral, intake, assessment and support. They offer services for individuals, their family and friends, general practitioners, other health professionals, and business and community groups.

To contact ADIS, ring the 24 hour hotline on 1800 250 015 and you will be automatically directed to the ADIS in the state or territory you are calling from.