There are both potential therapeutic uses for and potential
health risks of using cannabis (marijuana). A chemical called
delta-9-tetrahydrocannabinol (THC) is responsible for the way
your brain and body respond to cannabis. While it is used by
some for therapeutic purposes, there are short- and long-term
physical and mental health effects that can be harmful.

Short-term health effects

While cannabis may make you feel relaxed and happy,
you could experience unpleasant, unwanted or negative
effects on your brain and body.

Effects on the brain

The short-term effects of cannabis on the brain can include:
– confusion
– sleepiness (fatigue)
– impaired ability to:
– remember
– concentrate
– pay attention
– anxiety, fear or panic
– reduced ability to react quickly

Cannabis use can also result in psychotic episodes
characterized by:
– paranoia
– delusions
– hallucinations

Emerging evidence suggests that a chemical in cannabis
called cannabidiol (CBD) may help dampen some of the
psychoactive effects of THC1 such as:

1 Bhattacharyya et al. (2010) Opposite effects of delta-9-
tetrahydrocannabinol and cannabidiol on human brain function
and psychopathology. Neuropsychopharmacology 35(3): 764–74.
– disturbances in mood
– psychotic symptoms

There is also evidence to suggest that combining tobacco
with cannabis can increase:

– the strength of some psychoactive effects
– the risk of poor mental health outcomes, including dependence

Effects can be felt within seconds to minutes of smoking,
vaporizing or dabbing cannabis. These effects can last up
to 6 hours or longer.
If you eat or drink cannabis, these effects can occur within
30 minutes to 2 hours and can last up to 12 hours or longer.
Effects on the body
The short-term effects of cannabis on the body can include:

– damaged blood vessels caused by the smoke
– decreased blood pressure, which can cause people
to faint or pass out
– increased heart rate, which can be a danger for people
with heart conditions and can lead to an increased risk
of heart attack