Asthma and cannabis

Smoking cannabis is not good for our bodies. Research shows it can increase asthma symptoms and make breathing more difficult.


Most of us know that smoking tobacco is bad for our health, particularly our lungs. Asthma also affects our breathing and our lungs.

If you smoke cannabis, you may not be aware how this affects your lungs, and your asthma symptoms.

When people have asthma, their airways narrow, this is caused by:

  • Airways swelling
  • Airways becoming thick with mucus
  • The muscles around airways squeezing tight

This is why it is difficult for people with asthma to breathe.

Smoking cannabis has been shown to:

  • Increase mucus in the airways
  • Increase the number of glands that produce mucus
  • Damage the airway walls
  • Cause swelling in the airways

This means the space in the airway that air travels through is reduced due to the swelling and extra mucus.

  • You might recognise the symptoms that show you this is happening in your lungs:
  • Feeling out of breath
  • Tightness in the chest
  • Wheezing
  • Frequent coughing in the daytime or being woken at night by these unpleasant symptoms

Smoking cannabis increases these symptoms, and means you are more likely to have an asthma flare-up, or sudden or severe asthma attack.

There is no evidence supporting the use of cannabis in treating asthma in the long term.

Cannabis smoke

Cannabis smoke contains harmful chemicals including carcinogenic compounds (these are known to cause cancer) even more than tobacco smoke.

These chemicals damage the lungs and stop them from working properly.

We know this damage is increased in people smoking cannabis because of then longer, deeper breaths taken in with smoking cannabis, compared to tobacco.

People with asthma, who smoke cannabis, have more symptoms (feel worse, more often) and their asthma medications do not work as well.

Does cannabis smoke affect other people breathing it in?

There is little research available yet on the impact of cannabis smoke on other people. However, given cannabis smoke contains higher levels of harmful chemicals than tobacco smoke, it is recommended that precautions be taken, particularly around children and people with asthma, lung and heart issues.

Other health issues

Smoking cannabis is associated with many other health issues, including a higher risk of heart problems and strokes. Mental health issues are strongly linked with smoking cannabis, in particular addiction, psychosis and schizophrenia.This means that smoking cannabis is known to affect your physical and mental health.

If you do have any of these asthma symptoms, see your doctor for a lung health check.

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