A single cannabis joint has the same effect on the lungs as smoking up to five cigarettes in one go, indicates research published ahead of print in the journal Thorax.
The researchers base their findings on 339 adults up to the age of 70, selected from an ongoing study of respiratory health, and categorised into four different groups.
These comprised those who smoked only cannabis, equivalent to at least one joint a day for five years; those who smoked tobacco only, equivalent to a pack of cigarettes a day for at least a year; those who smoked both; and those who did not smoke either cannabis or tobacco.
All the participants had high definition x-ray scans (computed tomography) taken of their lungs and they took special breathing tests designed to assess how well their lungs worked.
They were also questioned about their smoking habits.
Seventy five people smoked only cannabis, and 91 smoked both. Eighty one people did not smoke either, and 92 smoked only tobacco.
Combined smokers tended to use less tobacco, the findings showed.
Cannabis smokers complained of wheeze, cough, chest tightness and phlegm. But emphysema, the progressive and crippling lung disease, was only seen in those who smoked tobacco, either alone or in combination.
But cannabis still damaged the lungs and stopped them from working properly.
It diminished the numbers of small fine airways, which are important for transporting oxygen and waste products to and from the blood vessels effectively.
And it damaged the large airways of the lung, blocking airflow, and forcing the lungs to work harder.
The extent of this damage was directly related to the number of joints smoked, with higher consumption linked to greater incapacity.
The effect on the lungs of each joint was equivalent to smoking between 2.5 and five cigarettes in one go.
The authors explain that the impact of cannabis is strongly associated with the way in which it is smoked. It is usually smoked without a filter, and at a higher temperature. Smokers tend to inhale more deeply and to hold their breath for longer.
Source: Effects of cannabis on pulmonary structure, function, and symptoms
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Pubic Hair Grooming Common Among Some US Women
- How A Former Naturopath Can Help Unravel The Trickery of Alternative Medicine
- Some Celiac Disease May Be Due To Viruses
- Out Of Africa: What They Do Not Tell Us
- Brain Cancer: Why Glioblastoma Is So Difficult To Treat
- Can A New Rule Trigger A Second EU Referendum? Petition 4 Millon Signatures, Nearly 12% Of Total Votes Cast
- Swarm Bots Kill Mass Shooter
- "Science researchers did the CARET study, to see if vitamin A could chemo-prevent lung cancer (it..."
- "Whether or not a conclusion can be used for bad purposes should never be the reason to shut down..."
- "This is a shockingly racist, repulsive, pseudoscientific article. It is so depressing to find it..."
- "That's not what I asked. Instead you pulled the classic do your own research trick which means..."
- Vaccine against Zika virus tested successfully in mice
- The irony of awkward
- Aussie innovation changing how we experience the Tour de France and Rio Olympics
- An anti-apoE4 specific monoclonal antibody counteracts the pathological effects of apoE4 in vivo
- Thousands on one chip: New method to study proteins