ANNEX TO CHAPTER II HEALTH ADVICE ON CANNABIS

This book is about issues in cannabis policy, and is not primarily concerned with advice to individuals about their own or others’ cannabis use. However, we offer here brief advice about cannabis use in the light of the literatures we have just reviewed.

Anyone who is contemplating using cannabis and who wishes to avoid its most probable acute and chronic adverse health effects should abstain from using the drug. This advice is especially pertinent for persons with any disease or condition (e.g. cardiovascular or respiratory disease, serious mental illness or other types of substance abuse) which increases their vulnerability to its adverse effects.

The following advice could be given to cannabis users who do not intend to stop, but who wish to reduce their risks of experiencing adverse health effects.

•    They should not drive when intoxicated (that is within several hours of smoking a ‘joint’), and should especially avoid driving after combining alcohol and cannabis use, because their impairments may be additive.

•    They could eliminate the respiratory risks of cannabis use by changing from smoking to the oral route. If they persist in smoking cannabis, they should not use the deep inhalation and breath-holding technique which greatly increases the delivery and retention of particulate matter and tar. It is possible to minimise the harms of smoking by using a vapouriser.

•    Cannabis smokers who do not otherwise use tobacco should avoid mixing tobacco with cannabis when smoking a ‘joint’, if they wish to avoid developing nicotine dependence and the substantial and well-established adverse health effects of tobacco smoking.

•    Cannabis users could minimise the risks of dependence by reducing their frequency of use to weekly or less often, and by avoiding daily use which carries the highest risk of dependence.

•    Evidence is emerging that cannabis with high THC and low CBD levels may carry extra risk of psychological harms. High THC and low CBD levels are most commonly found in the genetically-modified and hydroponically-grown forms of cannabis (‘skunk’).

•    Pregnant women should not smoke cannabis to avoid reduced birth weight.

•    There is a convergence of evidence suggesting that initiating cannabis consumption before the age of 17 significantly increases the likelihood of experiencing adverse effects, both personal and social. Children should therefore be advised of these risks.