CASEBOOK: CANNABIS CAN HARM LUNGS OF RUNNERS

I have been running for seven months, which has helped me to give up
smoking and eat more healthily.

I run five miles a day four times a week, usually with a gap between Friday
and the following Tuesday, mainly because as part of my weekend wind-down I
smoke cannabis, and this makes me feel too lazy to do anything energetic.

Apart from lethargy I do not feel any ill-effects, but can you tell me
whether, in the longer term, it could be detrimental to my health or
ability to run long-distance? I am a 23-year-old male.

Giving up cigarette smoking is perhaps the most important thing that anyone
can do to improve their health, says Dr Timothy Anstiss, medical director
of Strategic Health, a healthcare consultancy. As regards the longer-term
implications of smoking cannabis, you are not alone in your uncertainty, as
a number of different groups with varying agendas send out contradictory
messages.

Furthermore, identifying any adverse effects is complicated by the fact
that cannabis smokers commonly use tobacco, so untangling the potentially
harmful effects of cannabis from those from tobacco can present difficulties.

As with many other drugs, the harmful effects are related to the pattern
and circumstance of use. However, inhaling any hot, smoky substance into
delicate tissues such as the lungs is probably unhelpful, and research
shows that smoking marijuana can cause inflammation of the airways and
bronchitis. One study concluded that the regular smoking of marijuana by
young adults is associated with significant airway inflammation that is
similar in frequency, type, and magnitude to that observed in the lungs of
tobacco smokers and can produce respiratory symptoms (coughing, wheezing
and sputum production) like those experienced by cigarette smokers.
Although increased risk of developing mouth, throat and lung cancer is not
proven, cannabis smoke does contain carcinogens. Smoking cannabis may well
be harmful to the heart for those with pre-existing heart disease and is
probably harmful during pregnancy.

The psychological harm caused seems to vary. Studies of long-term users in
non-treatment community samples indicate that a number are dependent on the
drug, with one in ten who wants to stop or cut down finds it difficult.
Cannabis is known to cause doserelated changes in psychomotor performance
impairing driving and academic performance, and a reasonable number of
users report short-lived adverse psychological effects including psychotic
states following heavy consumption. Chronic users also show subtle
impairment in memory, organisational abilities and attention span, and the
effects become more pronounced the longer the duration of use. Permanent
brain damage has not been proved but there is concern that cannabis may be
a "gateway drug". It is typically the first illicit drug used by those who
develop problems with heroin and cocaine.

Your lung function is probably going to be impaired if you continue to
smoke cannabis, so if you want to fulfil your potential as an athlete,
stopping will help. The increased likelihood of getting chest infections
will also interfere with your ability to train, as would a psychotic
episode or the worsening of any severe mental illness.

Your weekend break from running is also probably too long; your performance
may continue to improve, but you would do better with a proper training
schedule.

Send your Casebook questions to Jennai Cox, Fit to Play, Sport, The Times,
1 Pennington Street, London E98 1TT or email jennai.cox@thetimes.co.uk