CANNABIS JOINT 'CAUSES THE SAME LUNG DAMAGE AS FIVE CIGARETTES'

Taking one cannabis joint causes as much damage to the lungs as
chain-smoking up to five cigarettes, a new study has found.

Airflow obstruction from taking the drug is thought to be exacerbated
by no filter, and the tendency among cannabis smokers to inhale more
deeply and hold the smoke in for longer.

The study of 339 adults up to the age of 70 found cannabis smokers
complained of wheezing, coughing, chest tightness and phlegm, and the
effects of one joint is equivalent to smoking between 2.5 and five
cigarettes in a row. The results are due to be published in the
medical journal Thorax.

However, the researchers, including Professor Richard Beasley from the
Medical Research Institute of New Zealand, found people who smoked
cannabis without tobacco did not suffer from emphysema - a serious
lung disease. The 339 volunteers were divided into four groups:
cannabis only (75 people); combined cannabis and tobacco (91); tobacco
only (92) and non-smokers of either substance (81).

Cannabis smokers were included if they had taken at least one joint a
day for five years, while tobacco smokers were involved if they had
taken the equivalent of 20 cigarettes per day for 12 months.

All the volunteers had high-definition X-rays of their lungs and took
part in breathing tests to assess their lung function. They were also
asked about their smoking habits. The experts noted that the drug
diminishes the numbers of small, fine airways that transport oxygen
and waste products to and from blood vessels. Cannabis is also linked
to damage in the large airways of the lung, blocking airflow and
forcing 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, said the
researchers. They concluded: "The most important finding was that one
joint of cannabis was similar to 2.5 to five tobacco cigarettes in
terms of causing airflow obstruction.

"This dose equivalence is consistent with the reported three to
fivefold greater levels of carboxyhaemoglobin (a marker of carbon
monoxide exposure) and tar inhaled when smoking a cannabis joint
compared with a tobacco cigarette of the same size.

"This pattern is likely to relate to the different characteristics of
the cannabis joint and the way in which it is smoked. Cannabis is
usually smoked without a filter and to a shorter butt length, and the
smoke is a higher temperature. Furthermore, cannabis smokers inhale
more deeply (and) hold their breath for longer."

The findings follow research published last week which showed cannabis
could more than double the risk of illnesses such as schizophrenia.
Researchers found any use of cannabis, even taking the drug just once,
was associated with a 41% greater risk.

Campaigners have renewed calls for the government to reverse its
decision to downgrade cannabis to a class C drug.