Cannabis

Cannabis sativa, or marijuana, is the most widely used illegal drug in Canada. It is commonly used in three forms: the dried leaves and buds of the plant, and resin extracts known as hashish and hash oil.

The cannabis “high” comes from a chemical called THC (delta-9-tetrahydrocannabinol). In recent years, new growing methods have produced stronger marijuana. Hashish is usually stronger than marijuana, and hash oil is typically even stronger.

Effects on general health

Chronic marijuana users are at increased risk for cognitive difficulties including impairment of memory, attention, concentration and judgment.

Smoking marijuana may cause chronic inflammatory and precancerous changes in the airways and bronchial tissue. Although marijuana smoke contains several known carcinogens and tar that is more potent than that in tobacco smoke, the active ingredient, THC, is not itself cancer-causing. However, THC is an immunosuppressant, which means that it weakens the body’s natural defenses against cancer and other diseases. There is evidence that cannabis has both tumour-causing and anti-tumour properties. There is much yet to be known about the relationship between marijuana and cancer. So far, there is no evidence that suggests marijuana can be used without adverse health consequences.

It is unclear whether heavy, long-term marijuana use may trigger “amotivational syndrome,” a condition in which the user becomes lethargic and lacks interest in work, relationships, personal health or sex. However, there is some evidence suggesting a connection between marijuana use and depression.

Many people who use cannabis heavily for a long time have problems with short-term memory, concentration and abstract thinking. When long-term heavy use is abruptly stopped, withdrawal symptoms such as loss of appetite, upset stomach, nausea, sweating, irritability, anxiety and troubled sleep may occur. Most symptoms eventually subside after substance use is terminated.

Effects on women's health

Some evidence suggests that marijuana use among women may lead to the disruption of menstrual cycles and the risk of fertility problems.

Effects during pregnancy

There is no known safe level of cannabis consumption for pregnant women. It is not clear whether a child’s health problems are caused directly by a mother’s use of cannabis during pregnancy or in combination with other factors including

• poor nutritional habits
• smoking
• alcohol consumption
• use of more than one drug
• sleep problems
• a mother's general health prior to pregnancy
• genetics
• how much alcohol, tobacco or other drugs are consumed during pregnancy
• at what stage in the pregnancy the substance is consumed
• how long the substance has been used
   

The effects of drugs such as cannabis have been difficult to study because these other factors also affect pregnancy. However, it is safest to avoid alcohol, tobacco and other drugs during pregnancy.

Effects on the fetus

Women who use cannabis during pregnancy are at increased risk for premature labour and birth.

The chemicals in cannabis can pass from the mother to the child through the placenta, and may affect the finer development of neurotransmitter systems, affecting behaviour patterns. Neurotransmitters relay signals between nerve cells, and are what make the nervous system function.

Babies born to mothers who use marijuana during pregnancy are more likely to be smaller than other babies. Marijuana-exposed infants are at increased risk for decreased body length and low birth weight.

Having a small baby does not make labour and delivery easier. On the contrary, a smaller baby is not strong enough to help in its delivery, which complicates labour. Low-birth-weight infants are also more likely to have health problems as they grow.

Effects on breastfeeding

Using marijuana and breastfeeding is not recommended.

THC transfers through mother’s milk to the breastfeeding child. The effects of cannabis exposure through breast milk on an infant remain unknown, although some evidence suggests that nursing infants exposed to THC in breast milk may have decreased motor development.

Effects on child development

Prenatal exposure to marijuana, especially in the second trimester, has been associated with shorter stature.

Marijuana use during pregnancy can lead to hyperactivity, impulsivity and inattention in children. Children exposed to marijuana prenatally may also be at risk for decreased cognitive functioning and deficits in learning and memory. These developmental problems may be responsible for the link between prenatal marijuana exposure and academic underachievement in children.

Children exposed to marijuana in the first and third trimesters tend to have significantly increased levels of depressive symptoms within the first 10 years of life. Children exposed to marijuana before birth may also be at higher risk for leukemia, brain tumours and skeletal muscle cancer.

Not everything is known about the effects of alcohol, tobacco and other drugs on child development. It is safest to avoid using them during pregnancy.