What is Cannabis? Health Effects, Risks and Use | Drug Aware

Is cannabis different to synthetic cannabis? 

Yes! Synthetic cannabis refers to products containing a herbal mixture that is laced with a range of artificial chemicals used to try to copy THC.⁴  This drug is not cannabis at all.

For more information, visit our page on synthetic cannabis. 

How is cannabis used? 

Cannabis comes in these main forms:

1. Herbal cannabis (marijuana) – this is the dried leaves and flowers of the cannabis plant and is the weakest form;
2. Cannabis resin (hashish) – the dried resin from the cannabis plant; and
3. Cannabis oil (hashish oil) – the oil extracted from the resin and is the most potent form.³
4. Edibles – parts of the cannabis plant that are combined with food ingredients so they can be eaten.³

Cannabis (both marijuana and hashish) is usually smoked in a hand rolled cigarette known as a joint, smoked using a water pipe or bong or can be ‘spotted’ – which heats the hashish and the vapours are inhaled.¹ Cannabis can also be used in vaporisers and cooked into foods and eaten.¹  Cannabis oil is generally applied to cannabis herb or tobacco and smoked or heated.²

How long do the effects last? 

• There is a dose-response relationship between cannabis use and its effects, meaning the more that is used the stronger the effect will be. Effects will also last longer with larger doses.⁵
• Inhalation by smoking or vaporization releases THC into the blood within minutes, peaking at 15 to 30 minutes. The effects then begin to wear off within two to three hours. The person using can still feel impaired (e.g. slow to respond, confused) for two to six hours after use.⁶
• Effects on cognitive function (learning, thinking, memory, problem solving, attention, decision making) and coordination can last up to 24 hours.
• Short term memory impairment may last for several weeks.⁵
• After eating cannabis, effects can usually be felt in 30 to 90 minutes, with the peak of effect at two to three hours. The effects may last for four to twelve hours.⁷

For information on how long cannabis can be detected in your system visit the drug testing page. 

Can you overdose on cannabis? 

No. The amount required to cause an overdose in humans is far greater than the amount of cannabis that someone could use in a day.⁸

Who, and how many people use cannabis? 

Cannabis is the most widely used illicit drug in Australia. In 2019, approximately one in 10 (11.2%) Western Australians had recently* used cannabis.⁹  The average age of first use was 18.9 years and people aged 20 to 29 were most likely to have recently used cannabis.¹⁰

For more information on how many people use cannabis visit the Drug Statistics page.

*Recently means at least once within the last 12 months.

Short Term Effects 

Evidence has shown the most common short-term effects are: ^5,8,12

• mild euphoria, relaxation and reduced inhibitions;
• a tendency to laugh and talk more than usual;
• feelings of hunger;
• reddened eyes;
• perceptual alterations, hallucinations, intensification of ordinary experiences and changed perceptions of time, sound, colour, distance, touch and other sensations;
• increased heart rate;
• increased respiratory problems including asthma;
• anxiety;
• panic reactions, restlessness and confusion;
• feelings of cognitive impairment including attention, memory, balance, reaction time, information processing and perceptual motor coordination; and
• psychotic symptoms at high doses (e.g. hallucinations, paranoia).

Cannabis and driving 

In Western Australia, it is against the law for anyone to drive whilst under the influence of an illicit drug as per the Road Traffic Act 1974. Using cannabis makes driving more dangerous. This is because cannabis use can cause slow reaction-time, information-processing, and also impact on perceptual-motor coordination, motor performance, attention and tracking behaviour.⁸  Someone driving a car after using cannabis is at double the risk of having a car accident.⁸ This risk increases by a lot more if alcohol has also been used.⁸

Long Term Effects - What are the physical health risks? 

People who use cannabis regularly are more likely to also use alcohol, tobacco and other drugs, therefore it is hard to isolate cannabis as the main cause of certain medium to long term health risks.⁸  Doses of THC and how often people use is also hard to measure.⁸  However, researchers often use methods that allow for meaningful conclusions to be made.

Long term effects depend on the person who uses, how the cannabis is used, how often it is used and its strength. Long-term health effects of regular cannabis use may include:

• Chronic bronchitis^8,12 
• Cognitive impairment (from regular use that begins in adolescence)⁸

Possible negative effects of regular cannabis use (the causal relationship is unknown):

• Impaired respiratory (lungs) function¹²
• Respiratory and testicular cancer¹²
• Heart attack¹
• Stroke¹

The Brain 

We know there are many of the receptors that respond to THC located in the brain, including in areas that control attention, decision-making, motivation and memory.¹  Research has found reduced ability in verbal learning, memory and attention in people who use cannabis regularly. This is often related to how long and how often cannabis has been used, the age use started, and the amount of THC received.⁸

Heart attack and stroke 

We know that two cannabinoid receptors CB1 and CB2 are found in the cardiovascular system (heart and blood vessels).¹  Cannabis smoking by middle-aged adults may increase the risk of experiencing a heart attack.^1,8  There is some evidence that long-term, heavy cannabis smoking is associated with stroke in young people.¹

Cancer

THC and other cannabinoids are not cancer-causing agents. Cannabis smoke has been shown to cause cancer, given the damage it causes to cells, particularly the tiny and delicate cells in the lungs. However other mechanisms may reduce this effect. It is hard to quantify the exact level of risk of cancers of the lung and the upper digestive tract (mouth, tongue, oesophagus) and bladder associated solely with cannabis smoking.⁸  This may be because people who smoke cannabis often mix in tobacco when they smoke or also use cigarettes.

There is some suggestive evidence that testicular cancer is linked to cannabis smoking but more research is needed.^1,8

Dependence 

In Australia, cannabis dependence is the most common type of drug dependence after alcohol and tobacco.¹²  It is estimated that one in 10 of all people who use cannabis, and one in six people who begin use in adolescence will develop dependence.^12,8  Cannabis dependence is a group of behavioural, cognitive, and physical symptoms that develop after repeated cannabis use. It is generally characterised by:^1,5,8

• a strong desire or compulsion to use;
• difficulties in cutting down, changing or stopping use;
• a withdrawal state when cannabis use is stopped or reduced;
• tolerance; which means more of the drug is needed to produce the same effect;
• reduced interest in other activities because of cannabis use or recovery; and
• continued use despite obvious negative consequences.

Schizophrenia, psychosis and bipolar 

There is strong evidence to show the association (not a cause of) between cannabis use and an increased risk of the development of schizophrenia and psychosis.^12,13  There is a dose-response relationship, meaning the highest risk is among people who use more often.^13,14,15  Regular cannabis use doubles the risks of experiencing psychotic symptoms and conditions, especially if:

• an individual has a personal or family history of psychotic conditions; and
• if cannabis use begins in mid-teens.⁸

Cannabis use is associated with poor outcomes in people who already have an existing psychosis diagnosis.⁵ For those who have experienced episodes of psychosis, using cannabis can trigger further episodes of psychosis, worsen delusions, mood swings, hallucinations and feelings of paranoia. It may also play a role in not sticking to medication and treatment plans.⁵ Young people with a first episode of psychosis who stop using cannabis have better outcomes than those who continue to use. This includes less psychotic symptoms and better social functioning.⁵ 

In people diagnosed with bipolar, there is some evidence that shows a link between regular cannabis use and increased symptoms of hypomania and the more severe mania.¹³  There is some limited evidence which shows the association between cannabis use and the development of bipolar, especially among people who use regularly.¹³

Depression

There is moderate evidence that suggests cannabis use is associated with a small increased risk of depression in people who have ever used cannabis.¹³  There is a slightly higher increased risk of depression for people who use cannabis daily.¹⁵

Anxiety 

Short-term effects of anxiety and panic reactions are reported among people who use cannabis, particularly people who have not used or not used much before.⁸  There is emerging evidence associating cannabis use with anxiety conditions and symptoms of anxiety. The current level of evidence is not yet strong enough to say cannabis causes anxiety.^5,13  However, there is moderate evidence of an association between regular cannabis use and an increased risk of social anxiety conditions.¹³

Suicide 

There is moderate evidence that’s shows an association between cannabis use and an increased number of people experiencing suicidal ideation and suicide behaviour.¹³

Do different types of cannabis affect mental health differently? 

To some degree yes - this is to do with the chemicals that make up the cannabis and the way it is used. 

Since 2000, there is evidence that the THC content of cannabis is increasing.⁸  A higher THC content may increase anxiety, depression and psychotic symptoms in people who haven’t used before or haven’t used much.⁸ It may also increase the risk of dependence and psychotic symptoms in people who use regularly.⁸  More research is needed in this area. 

Some of the cannabinoids such as CBD may reduce the psychoactive effects of THC.¹  There is currently lots of research being done on what cannabinoids, including THC, could be used to help with medical conditions, but the evidence for this, especially for mental health, is not clear yet.^16,17

Using cannabis with other drugs

Using cannabis with other drugs increases the risk of something going wrong. If cannabis is used with other depressant drugs (such as opiates) the depressant action generally increases. When cannabis is combined with alcohol it can frequently lead to behaviour which causes injuries. Cannabis can also interact with over the counter or prescribed medication. Always talk about the risks with your health professional.

Cannabis and pregnancy 

Women should not use cannabis while pregnant, or while trying to become pregnant.⁸  Cannabis use during pregnancy has been shown to reduce a baby’s birthweight.^12,18  Low birth weight is linked to an increase in disease and death in infants. Long-lasting effects of low birthweight can include: neurosensory conditions; decrease in height; decreased IQ and educational achievement and mental health conditions.¹⁸

Cannabis for medicinal use 

Cannabis for medical use is legal in Western Australia. This must be prescribed by a doctor and dispensed by a pharmacy. It does not include cannabis that you can smoke. It also does not produce the psychoactive effects of cannabis.

In February 2016, the Australian Government amended the Narcotic Drugs Act 1967 to allow farming of cannabis for medicinal or scientific purposes, under a national licensing scheme. Medicinal cannabis products are only available for specific patient groups under medical supervision. Any doctor in Western Australia can prescribe medicinal cannabis if they believe this treatment is suitable and provided they have the required Government approvals. Prescriptions for medicinal cannabis can be dispensed at any pharmacy in Western Australia. It is important to note that cannabis grown for other purposes (other than for industrial hemp) remains illegal and it does not allow the personal or home cultivation of cannabis for use in medical conditions.²⁰

The Therapeutic Goods Administration’s webpage on ‘Guidance for the use of medicinal cannabis in Australia: patient information’ provides a broad overview of the current evidence to support using medicinal cannabis for certain conditions. It also highlights the cautions surrounding treatment, how medicinal cannabis can be prescribed and future research.

For more information visit the Office of Drug Control.

What is the difference between decriminalisation and legalisation? 

Decriminalisation 

Decriminalisation is not legalisation. If drug possession and personal use are decriminalised, it is still illegal to possess and use drugs. Selling and manufacturing drugs still carry criminal penalties.

When drug use and possession are decriminalised, criminal charges are not applied. Criminal charges are those brought against a person by police and legal practitioners on behalf of the government. They are managed through the court system. If a person is found guilty and convicted, punishment may include jail time. The person will also have a criminal record.²⁰

Decriminalisation may replace criminal penalties with civil penalties. These could include no penalties, referral to an education or treatment program, or a fine.²¹  Civil cases do not have to go through the court system and may be dealt with by tribunals. This also means the person won’t have a criminal record which can affect employment, housing and travel opportunities.

Did you know, WA has had a period when the personal use of cannabis and the growing of two plants was decriminalised? This legislation was revoked in 2011.

Legalisation 

Legalisation is the process of removing all penalties for possession and use of a drug. Cannabis would then be available to the adult general population for purchase and use at will, similar to tobacco and alcohol that have regulations to manage where and how the legal drug can be produced, sold and consumed.²¹

However, just because a drug is legal, does not mean it is safe. For example,  alcohol causes the most harm than any drug in Australia. ²²

When should I seek help? 

If you can’t stop or cut down on your own, or if your cannabis use is affecting your relationships, your ability to work or study or your health in other ways such as your lung health (coughing, wheezing, shortness of breath) or your mood then go have a chat and a check-up.⁷

Tips for trying to cut down or quit cannabis 

Some helpful tips for cutting down or quitting your cannabis use:²³

• Make a list of the advantages quitting cannabis will have for you. Whether it’s saving money, better health, having more energy and motivation or having fewer arguments with your family - keeping these advantages as reminders can help keep you on track!
• Delay having your first smoke of the day for a few hours and gradually increase this delay.
• Do something else so you are not concentrating on using cannabis. Go for a walk, see a friend who doesn’t use cannabis or go to the gym. Delaying use by doing something else when you are craving cannabis, allows time for the urge to pass.
• Set limits on what times, days and amounts you use.
• Distance yourself from cannabis and the triggers associated with using cannabis.
• Stop buying cannabis and decrease or minimise contact with your friends who are still using cannabis.
• Throw out all pipe and bongs, or other things you have that you would use cannabis in.
• Set a date when you want to be quit by, get support from family members or friends. Make sure they are aware you are trying to quit so they can be there to help and support you.
• Consider seeing your GP or a psychologist. Some people may benefit from this especially if the withdrawal symptoms are making it difficult for them to continue to not use or if the reasons for their use in the first place are psychological. Some people may need some level of medication to cope with withdrawal symptoms. Often, around six to eight weeks after quitting, some of the symptoms of anxiety and depression can lift because the anxiety or depression were being made worse by the cannabis use.
• Sometimes it can help to speak to someone, whether a family member, or a friend, or even a qualified drug counsellor, they are there to support you.
• Sometimes making a statement about choosing to use can often provide the necessary personal agency to delay. “I have a choice. I can choose to use or choose not to use.” This concept can be hard to achieve as often those dependent on cannabis do not see using as a choice but a necessity.

Withdrawal 

The most common withdrawal symptoms that are severe enough to impact on everyday functioning include anxiety, insomnia, appetite disturbance, and depression.^8,23

Getting through withdrawal can be easier if you take it one day at a time and focus on activities that help you cope with the effects of withdrawal. Knowing what to expect can help you get through. The more someone is using when they stop, the more intense their withdrawal. This starts on day one, peaks on days two to four and is over for most people after five to 10 days, though sleep problems and moodiness can continue for several weeks.²³

Following are some tips on how to cope with the various withdrawal symptoms you may experience:⁷

• Cravings to use. These can be quite strong and if you feel anxious then this can intensify your cravings. Sometimes hunger will also be confused with having a craving. Make sure you eat regularly and ensure you are properly hydrated.
• Irritability. It is very common to get irritable and agitated during withdrawal, so it will be important to do things that help you relax. Taking a few deeper breaths, taking a break from the situation that is causing the agitation can sometimes work. Self-talk is also important. “I know I am irritable as I am quitting cannabis. What can I do to lessen my irritability?”
• Sleep disturbance. This can occur if it is normal to fall asleep stoned/under the influence/intoxicated, so when stopping smoking cannabis some may find it harder to fall asleep. Sleep is a habit and so it will require the person to get used to sleeping without cannabis. You may also find that when you stop smoking you often tend to dream more or at least remember your dreams more. Learning meditation and relaxation techniques can be very handy here.
• Feeling nauseous or losing your appetite. This may be related to the fact that cannabis can increase your appetite. So it would make sense that you may feel a bit sick because you are used to the way cannabis affects your appetite. Try and eat things you like, make sure they are not too spicy or rich which could increase nausea. Take regular small snacks and remember to keep hydrated. Sometimes ‘fizzy water’ can be very refreshing.
• Feelings and reactions of anger, depression and/or grief. These emotions can occur as they are due to the interrelated physical and psychological dependence on the effects of the drug.

Some people may become very dependent on the way that cannabis makes them feel, so when they stop using it, it can be very difficult.

Don’t be afraid to ask for support or help to plan your quit attempt. Don’t give up if you slip up - a slip up is not a relapse. Consult with your GP or other qualified health professional if you have any concerns about your withdrawal or call the Alcohol and Other Drug Support Line.

Last updated: February 2022