Health effects

Short-term effects

The effects of smoking small amounts of cannabis include:

  • relaxation and loss of inhibition
  • increased appetite
  • altered sensory perceptions, visual, auditory and tactile
  • loss of coordination
  • impaired thinking and memory
  • talkativeness
  • drowsiness
  • decreased nausea
  • dryness of eyes, mouth and throat
  • red or bloodshot eyes.

Greater quantities of cannabis can cause unpleasant effects, including:

  • confusion
  • mild hallucinations
  • paranoia
  • impaired coordination
  • restlessness
  • depression.

Long-term effects

There is research evidence that there are some negative effects of long-term, regular cannabis use.

  • Respiratory illness: Smoking cannabis presents similar health risks to smoking tobacco. Smoke releases carcinogens that can affect the respiratory system, and risk increases for cannabis smokers because they tend to inhale more deeply and hold the smoke in longer. However, the amount of cannabis smoked, compared to tobacco, tends to be less.
  • Brain function: The ability to learn and remember is impaired by regular cannabis use. Short-term memory is especially affected. Regular users also find it harder to concentrate.
  • Motivation: Regular users find it hard to stay motivated for sport, school and work, and their energy levels suffer. These effects do diminish over time after cannabis use is stopped.
  • Hormones: There is evidence that cannabis affects a person’s hormones. Regular users sometimes report a lower sex drive, irregular menstrual cycles for women and lower sperm counts for men.
  • Immune system: There is emerging evidence that regular cannabis use may harm the immune system.
  • Mental health: There is growing evidence linking cannabis use and mental illness. Individuals who are susceptible to mental illness put themselves at greater risk of psychotic symptoms when using cannabis. Cannabis also appears to make psychotic symptoms worse for people with schizophrenia. 
  • Drug-induced psychosis can also result from heavy and prolonged use of cannabis. Symptoms include hallucinations, delusions, memory loss, and confusion, and can last up to several days.

Currently there is no evidence to suggest that occasional use of small amounts of cannabis causes any permanent damage.