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Cannabis is a greenish or brownish material consisting of the dried flowering, fruiting tops and leaves of the cannabis plant Cannabis Sativa. Symptoms of “being high” on cannabis include decreased attention span, increased heart rate, slowed reaction times and a lack of a sense of time. These symptoms can last several hours. Sometimes less enjoyable symptoms – like nervousness or paranoia – can be experienced.

Common Terms

Marijuana – Another name for the Cannabis plant.

Cannabinoids – Chemicals that act on cannabinoid receptors.

Delta-9-tetrahydrocannabinol (THC) – The psychoactive component on marijuana.

Cannabidiol – One of the cannabinoids in the marijuana plant; not psychoactive.

Cannabis and Cognitive Functioning and Mental Health

Chronic cannabis use does not appear to produce significant, lasting cognitive impairments (problems with memory, attention, or other cognitive problems) in adults.


  • Starting cannabis use early (prior to mid-20s in age), while the brain is still developing, may lead to more lasting problems
  • Although the cognitive deficits resulting from chronic cannabis use have been shown in certain cases to be reversible after a month of discontinued use in adults, the same may not be true for those who start using cannabis in early adolescence

Cannabis and Respiratory Effects

Cannabis contains many of the same poisons and cancer-causing chemicals as tobacco smoke, and THC may make the lungs and airways more susceptible to respiratory problems.

Research suggests smoking cannabis may be even more harmful to a person’s airways and lungs than smoking tobacco.

People tend to inhale deeper and hold the smoke in longer.

Those who regularly smoke cannabis commonly report coughing on most days, wheezing, shortness of breath after exercise, chest tightness at night, sounds in their chest, early morning phlegm and mucus, and bronchitis.

Quitting cannabis smoking can reverse some of the negative respiratory symptoms experienced by those who smoke cannabis.

Cannabis and Driving

Definition: Drug-impaired driving refers to the operation of a motor vehicle, including snowmobiles, all-terrain vehicles, boats, trains and airplanes, while one’s ability is adversely affected by a drug, including illegal drugs, prescription drugs, over-the-counter medications and volatile inhalants such as toluene or nitrous oxide.

  • Cannabis impairs the cognitive and motor abilities necessary to operate a motor vehicle and doubles the risk of crash involvement
  • After alcohol, cannabis is the most commonly detected substance among drivers who die in traffic crashes in Canada
  • The police have the tools and authority required to detect and arrest drivers who are impaired by cannabis
  • Among young drivers in Canada, driving after using cannabis is more prevalent than driving after drinking
  • Males are three times more likely than females to drive after using cannabis

Cannabis and Fertility, Pregnancy, Breastfeeding and Parenting

These possible negative effects are:

  • Cannabis use may affect the ability to become pregnant. For example, heavy cannabis use has been linked to changes in menstrual cycle for women, and lower sperm count and poorer sperm quality in men
  • Some studies have shown that cannabis use may have some negative effects on pregnancy. For heavy cannabis users, and those who also use tobacco, cannabis may increase the risk of preterm birth
  • Smoking cannabis can reduce the supply of oxygen and nutrients to the fetus. Some studies show effects on the newborn such as lower birth weight, lower alertness and slower growth of the new baby. Cannabis has not been linked to birth defects. However, the effects on the developing brain may be lasting, as the baby grows to an adolescent and adult
  • When a breastfeeding mother uses cannabis, THC passes into the breast milk and is taken into a baby’s fat cells and brain. It can be stored for weeks. Some research found that infants exposed to THC through breast milk had slower motor development (affects baby’s movements and responses). More studies are required to determine the true effect of cannabis exposure when breastfeeding
  • As a result of exposure to cannabis during pregnancy a child may have difficulties with learning, behaviour and mental health in later life

For more complete information on Cannabis and other drugs on pregnancy, the Society of Obstetricians and Gynaecologists of Canada have a great summary page.

Reduce Your Risk

Cannabis use is a personal choice, but it comes with risks to your health and well-being. Follow these recommendations to reduce your risks.