"Discussion about cannabis smoking, whether among the student population or older, and whether inhaled or not, is a relic of earlier puritanical generations. What really matters is its long-term effect on both physical and mental health. Recent research has confirmed that cannabis smoking may induce psychotic-type breakdowns, and relatively frequently unmasks latent hereditary psychiatric disease, as well as causing psychological changes.
"A report by leading Swedish scientists in 1998 - not a group that would be thought of as natural conservatives - summarised the psychological and psychiatric problems that may be induced by its use. They concluded: 'Cannabis is one of the most psycho-pathogenic of all psychotic preparations. Compared with heroin abuse, cannabis smoking, in addition to the strong grip which develops with dependence, is associated with the far more serious risk of developing mental disorders of various kinds."'
"A person who suffers a psychotic breakdown after cannabis, had he not smoked it, might well have journeyed happily through life being no more than mildly eccentric. Research indicates that one person in four has the genes that might make them vulnerable to cannabis. Disturbingly, research has also shown that to inherit various packages of genes that might be associated with a vulnerability to cannabis is not rare. Cannabis's adverse effects may be dose-dependent but there is no way of determining who these people are. Cannabis will also cause psychological changes. These include poor memory, shortened attention span and lack of judgment and/or insight, as well as apathy, although the extent of this symptom is disputed.
"The physical effects of cannabis include damage to the immune system, the lungs and the oral and nasal spaces. This last association accounts for the clear link between smoking cannabis and an increased incidence of head and neck cancers. Cannabis has an adverse effect on the reproductive system in men and women. In women it may cause ovulatory and menstrual irregularities, and in men can cause testicular atrophy with a marked reduction in sperm count.
"The babies born to cannabis-smoking couples are, on average, shorter, have a lower birth weight and reduced head circumference, and after delivery are more restless and nervous. As children they have an appreciably higher incidence of one form of leukaemia, have poorer memories and verbal ability as toddlers, and do less well in intelligence tests up to the age of 9.
"In rodents there is an increased incidence of foetal abnormalities and stillbirths in those given cannabis. Similarly, a long-term project evaluating the effect of cannabis on rhesus monkeys, either before or during pregnancy, showed that it quadrupled the death rate of babies in utero or soon after birth. There was also a higher incidence of congenital neurological deformities. Although there have been reports of similar findings in humans, a relationship between cannabis and foetal abnormality is difficult to prove."
Dr Thomas Stuttaford [In The Times 24 October 2005]