Smoking cannabis frequently over a long period of time can damage your lungs, particularly if you hold the smoke in after inhaling. Daily or near-daily use of cannabis increases the risk of developing anxiety or depression, psychosis and schizophrenia. It could also affect your ability to become pregnant by disrupting menstrual cycles or reducing sperm count. Becoming dependent on cannabis is also a risk and many people who try to quit experience withdrawal symptoms such as irritability, sleeping difficulties, cravings and anxiety.

If you choose to use cannabis, the only way to avoid these risks is to use it infrequently, taking breaks from using cannabis, using products with lower levels of THC and higher levels of CBD, and limiting the amount of cannabis that you use in a single day.  For more information on reducing your risks, check out the Lower-Risk Cannabis Use Guidelines.

Effects on lungs

Smoking cannabis causes toxic by-products to be released, and inhaled, similar to those found in smoking tobacco cigarettes. Some studies show vaping reduces the toxins and carcinogens released into the lungs.

When using cannabis and tobacco together, you increase your risk of developing breathing problems. Smoking cannabis with tobacco could increase the risk of tobacco-related lung disease such as asthma, chronic obstructive pulmonary disorder (COPD) and lung cancer.

In places where cannabis has been legalized, edibles have become more popular than the traditional ways of using cannabis because they do not affect the lungs.1

Anxiety and depression

Research has shown that teenagers with high levels of anxiety might start using cannabis at a younger age, and they may increase the amount and frequency of use more quickly than other teens. Teen girls who experience depression may also use larger amounts of cannabis more often than peers. 

Frequently using cannabis to self-medicate for anxiety and depression, rather than developing healthy coping skills, can make it more difficult to recover from these problems.

There is conflicting evidence about cannabis and its effectiveness to treat anxiety. If you are using or considering trying cannabis to treat your anxiety or depression, speak to your health care provider.

Psychotic disorders

It is not recommended to use cannabis if you have a personal or family history of psychosis, schizophrenia, or bipolar disorder.

Most cannabis users will not develop schizophrenia, but for those already at risk of developing schizophrenia, either due to family history or other risk factors, cannabis can increase this risk. This is especially true if cannabis use starts when a person is young, or if a person uses cannabis frequently.

Chronic symptoms of psychosis may also appear when cannabis is used frequently or from an early age. These can persist even after cannabis use has stopped. This may not occur in every cannabis user, but using cannabis for long periods of time greatly increases a person’s risk.

For conditions like bipolar disorder, where periods of mania or psychosis may be triggered, cannabis increases the likelihood that these manic periods will occur.

Poor memory, concentration, and motivation

Frequent, long-term use of cannabis can negatively affect your memory, your ability to concentrate at school or work, and for some people will make it more difficult to become motivated. As a result, long-term cannabis use has been associated with lower grades and poorer work performance.


Addiction (or dependency) to any drug is a serious and often relapsing chronic disease.Cannabis use disorder is “a problematic pattern of cannabis use leading to clinically significant impairment or distress.”2 Dependency happens in about nine per cent of cannabis users, compared to alcoholism, which occurs in 23 per cent of users. People who have a cannabis use disorder can have a difficult time quitting or cutting back on use, or may experience withdrawal symptoms if they do. Withdrawal symptoms include anxiety, irritability, upset stomach, loss of appetite, disturbed sleep and depression.3

Signs of cannabis use disorder include:

  • craving cannabis
  • not completing important responsibilities at work, school or home;
  • giving up important social or occupational activities
  • using cannabis more often or in larger amounts to achieve the desired effects
  • having difficulty cutting down on or controlling cannabis use

If you or someone you know is struggling with a dependency, contact the youth addictions centralized intake service: 1-877-710-3999, or the Manitoba Addictions Helpline at 1-855-662-6605.

1Canadian Nurses Association, Harm Reduction for non-medical cannabis use, p. 6.
2Diagnostic and Statistical Manual of Mental Disorders, DSM-5.
3Canadian Nurses Association, p. 7.