The IQ is in smoke: the daily, Le Monde, whose 8 September issue examines the results of an important study published online last 27 August by the American journal Proceedings of the National Academy of Sciences on the result of research on the cognitive and long-term performance of young people who smoke cannabis, the most widely consumed illegal substance in the world. One thousand and thirty-seven individuals born between 1972 and 1973 were monitored over two decades by researchers in New Zealand and the United Kingdom in a study described as “prospective”, and exactly here a new aspect has emerged: so far studies that have followed, “in prospective” and for many years, such a large number of individuals, are few and far between.
If, on the one hand the cognitive effects of smoking hashish – such as disturbances of the memory, of attention and of concentration as well as the lack of motivation – were well known, the authoritative French newspaper reports, on the other, the vulnerability of an adolescent's brain to this drug has not been exhaustively researched. The shocking data resulting from the study are essentially two.
In the first place a decrease of up to eight points in intellectual performance measured by the IQ among those who began smoking cannabis at an early stage, that is, as teenagers, and who later became regular smokers – “at least four times a week” – over a long period. This decline in intelligence was not only noticed by researchers but also by the friends and family members of the young people concerned.
The second alarming fact that emerged is that while quitting or reducing intake of the drug prevented further impairment, it did not appear to restore normal mental functioning. In other words, the damage has proven to be irreversible and to have important effects on the daily life of adolescents.
This study is so interesting because it has demonstrated the interaction of cannabis with brain development, which, let us remember, is incomplete until the age of about 20. If one thinks that, at least in France, 24 per cent of 16-year-olds smoked marijuana at least once a month in 2011, it is easy to deduce the extent and gravity of the phenomenon. Quite apart from the fact that various studies have broadly documented other disturbing data.
To mention just a few examples, the risk of developing depression is five times higher in the case of cannabis abuse in an adolescent Amine Benyamina writes; the risk of the onset of an anxiety syndrome, in similar cases, is double, Sandrine Cabut writes, and even serious psychological pathologies, such as schizophrenia, seem to appear more frequently in those who use this drug, often superficially labelled “light”.
Data such as these are food for thought for those who live in a larger or smaller city and who often encounter young people, also at work. If we think of the delicate process of the personal development of a young individual we cannot but be left aghast at the thought of the sea of visual, auditive, affective, and at times, toxic stimuli to which he or she is constantly exposed.
What will be the result of this continuous misuse to which our society subjects itself, mainly for commercial purposes? It is probable that the effects, often amidst general indifference, will go far beyond what a mere IQ test can reveal, and that they will leave a deep scar on the person's whole development.