Effects of cannabis

The effects of any drug (including cannabis) vary from person to person. How cannabis affects a person depends on many things including their size, weight and health, also whether the person is used to taking it and whether other drugs are taken around the same time. The effects of any drug also depend on the amount taken.

There is no safe level of drug use. Use of any drug always carries some risk—even medications can produce unwanted side effects. It is important to be careful when taking any type of drug.

Immediate effects

  • loss of inhibition
  • spontaneous laughter
  • quiet and reflective mood
  • affected perception including sound, colour and other sensations
  • confusion
  • altered thinking and memory
  • anxiety
  • mild paranoia
  • altered vision
  • reddened/bloodshot eyes
  • relaxation
  • sleepiness
  • reduced coordination and balance
  • increased heart rate
  • low blood pressure
  • increased appetite.

Low to moderate doses

Low to moderate doses of cannabis can produce effects that last 2 to 4 hours after smoking. The effects of ingested (eaten) cannabis usually start within 1 hour. Some of the effects include:

Higher doses

  • confusion
  • restlessness
  • excitement
  • hallucinations
  • anxiety or panic
  • detachment from reality
  • decreased reaction time
  • paranoia.

Long-term effects

Long-term cannabis use can have many effects on an individual:

Brain: Impaired concentration, memory and learning ability.

Lungs: Smoking cannabis can result in a sore throat, asthma and bronchitis.

Hormones: Cannabis can affect hormone production. Research shows that some cannabis users have a lowered sex drive. Irregular menstrual cycles and lowered sperm counts have also been reported.

Immune system: There is some concern that cannabis smoking may impair the functioning of the immune system.

Mental health: Cannabis use, especially heavy and regular use, may be linked to a condition known as a “drug-induced psychosis”, or “cannabis psychosis”.

There is some evidence that regular cannabis use increases the likelihood of psychotic symptoms in people who are already vulnerable due to a personal or family history of mental illness. Cannabis also appears to make psychotic symptoms worse for people with schizophrenia, and using cannabis can lower the chances of recovery from a psychotic episode.

Other effects of cannabis use

Social problems

All areas of a person’s life can be affected by drug use.

  • Disagreements and frustration over drug use can cause family arguments and affect personal relationships.
  • Legal and health problems can also add to the strain on personal, financial and work relationships.

Taking cannabis with other drugs

The effects of mixing cannabis with other drugs, including alcohol, prescription medications and over-the-counter medicines, are often unpredictable.

When people drink alcohol and use cannabis at the same time, they may have strong reactions such as nausea and/or vomiting, panic or paranoia.

Some people use cannabis to come down from stimulants such as amphetamines or ecstasy. The mixing of cannabis and ecstasy has been linked to reduced motivation, impaired memory and mental health problems.

Pregnancy and breastfeeding

Cannabis can be passed on to an unborn baby through the placenta, or to an infant in breast milk.

Find out about the effects of cannabis during pregnancy and breastfeeding.


It is dangerous to drive after using cannabis. The effects of cannabis, such as altered perception, impaired coordination and sleepiness, can affect driving ability. It is especially risky to drive after drinking alcohol and using cannabis, as the combination can increase the effects described above.

Read more about the effects of cannabis on driving.

Cannabis use in the workplace

Under occupational health and safety legislation, all employees have a responsibility to make sure they look after their own and their co-workers’ safety. The effects of cannabis such as altered perception and impaired coordination can affect a person’s ability to work safely and effectively.

For more information, visit the Australian Drug Foundation