Cannabis, or marijuana, is an illegal drug. It comes in different forms including hash or hash oil. Cannabis smoke contains many of the same carcinogens as tobacco smoke, which is a cause of respiratory cancer. Cannabis is a depressant drug and may induce psychosis in some people.
Cannabis, or marijuana, is the most commonly used illegal drug. It comes from the Cannabis sativa plant. It can be smoked or eaten and comes in a variety of forms such as dried plant leaves and flowers (‘heads’), a crumbly light brown or dark brown resinous material called ‘hash’, or in the form of a very potent oil called ‘hash oil’.
The psychoactive chemical in cannabis that makes users feel ‘high’ is called THC (delta-9 tetrahydrocannabinol).
Types of cannabis
There are a variety of different forms of cannabis:
- Marijuana – is the most common and least concentrated form of cannabis. It is made from dried plant leaves and flowers. The flowers, or ‘heads’, are the most potent forms of the plant. Marijuana resembles chopped grass and ranges in colour from grey-green to greenish-brown. It is usually smoked in a waterpipe (bong), a pipe or in a hand-rolled cigarette (joint).
- Hashish – consists of small blocks of dried cannabis resin. Blocks range in colour from light brown to nearly black. The concentration of THC (delta-9 tetrahydrocannabinol) in hashish is higher than in marijuana.
- Hash oil – is a thick, oily liquid extracted from hashish and ranges in colour from golden-brown to black. It is usually spread on the tip or paper of cigarettes and then smoked. Hash oil is more potent than the other forms of cannabis.
Cannabis is a depressant drug
Depressant drugs do not necessarily make you feel depressed. Rather, they slow down the central nervous system and the messages going to and from the brain to the body.
Effects of cannabis use
The effects of cannabis are different for each person. The effect can vary according to the mood or atmosphere in which it is used. The immediate effects of cannabis can last approximately two to three hours and may include:
- A feeling of relaxation and sense of wellbeing
- Reduced concentration
- Decreased coordination
- Distorted perceptions of time, space and distance
- Increased heart rate
- Increased appetite
- Increased talkativeness
- Reddened eyes
- Impaired driving ability
- Anxiety and paranoia.
- Feelings of excitement
- Anxiety or panic
- Detachment from reality
Cannabis can cause psychosis
Research suggests that cannabis use can make existing psychotic symptoms worse. It may even bring on symptoms in people who are predisposed to psychosis if they have a personal or family history of the disorder.
It is also believed that cannabis use, especially if heavy and regular, may cause the person to experience psychotic symptoms that can last for a few days. These episodes often include visual or aural (hearing-related) hallucinations.
Risks for long-term use of cannabis
Cannabis may also have additional effects on long-term users, including:
- The risk of asthma, emphysema, shortness of breath, chest infections, and throat, mouth and lung cancers
- Poor concentration, memory loss and learning difficulties
- Depression of the immune system, which increases the risk of developing infections
- Serious mental illness, such as schizophrenia.
Cancer-causing (carcinogenic) substances
Cannabis smoke has a higher concentration of certain cancer-causing (carcinogenic) agents than the smoke from tobacco, and there is evidence to suggest that cannabis can cause cancers of the lung and the aerodigestive tract.
Young people who smoke heavily are more at risk
Generally speaking, people who start smoking cannabis earlier (early adolescence) and smoke heavily are more likely to experience negative consequences. This may lead to mental health problems, but may also lead to more general life problems, like conflict at home, school or work, financial problems and memory problems.
Tolerance and dependence with cannabis
A tolerance to cannabis can develop with regular use, which means the person has to take increasing quantities to get the same effect. Some people can become psychologically or physically (or both) dependent on cannabis.
How to prevent the negative health effects of cannabis
The best way to avoid the harmful effects of cannabis is to avoid its use, especially for people who have experienced a psychotic episode in the past or who have a family history of psychosis.
Where to get help
- DirectLine Tel. 1800 888 236 – for 24-hour confidential drug and alcohol telephone counselling, information and referral
- DrugInfo, Australian Drug Foundation Tel. 1300 85 85 84
- National Cannabis Prevention and Information Centre helpline 1800 30 40 50
- Your doctor
- Hospital emergency departments
- Drug and alcohol treatment centres
- Community health centres
- Family Drug Help – for information and support for people concerned about a relative or friend using drugs Tel. 1300 660 068
Things to remember
- Cannabis has many harmful effects on health.
- Cannabis is an illegal drug.
- Cannabis impairs the user’s driving ability.
- Avoid cannabis if you have had a psychotic episode or there is a history of psychosis in your family.
- Help is available 24 hours a day, seven days a week.
You might also be interested in:
Want to know more?
Go to More information for support groups, related links and references.
This page has been produced in consultation with and approved by:
(Logo links to further information)
Department of Health logo
Last reviewed: May 2013
Content on this website is provided for education and information purposes only. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your doctor or other registered health professional. Content has been prepared for Victorian residents and wider Australian audiences, and was accurate at the time of publication. Readers should note that, over time, currency and completeness of the information may change. All users are urged to always seek advice from a registered health care professional for diagnosis and answers to their medical questions.
Content on this website is provided for education and information purposes only. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your qualified health professional. Content has been prepared for Victorian residence and wider Australian audiences, and was accurate at the time of publication. Readers should note that over time currency and completeness of the information may change. All users are urged to always seek advice from a qualified health care professional for diagnosis and answers to their medical questions.
For the latest updates and more information, visit www.betterhealth.vic.gov.au
Copyight © 1999/2013 State of Victoria. Reproduced from the Better Health Channel (www.betterhealth.vic.gov.au) at no cost with permission of the Victorian Minister for Health. Unauthorised reproduction and other uses comprised in the copyright are prohibited without permission.