Dopey kids

A number of commentators (for example Yobbo) have criticised the view that the sale of alco-pops such as Mudslides and Breezers should be banned. I agree bans are clumsy, and unlikely to be effective, but I am sympathetic to the notion that the use of several drugs (alcohol, nicotine and cannabis), while harmful to all age groups, are possibly particularly harmful to people of age less than about 25. If bans are inappropriate - then at least people in this age group should be made aware of the particular risks. Perhaps advertising of such products should be restricted.

Neuroscience recognises that the human brain does not reach adult structure until around age 25. Tissue growth occurs throughout the brain in early childhood followed by a remodelling during teenage years - including refinement or pruning of cortical synapses (nerve connections) that ensures good connections are strengthened while less useful ones disappear. Pruning is accompanied by myelination that speeds neural connections and improves brain operation.

Remodelling continues beyond traditional adolescence and is concentrated in the cortex parts of the brain that regulate emotions and behaviour. Recent work suggests that adolescents are vulnerable to disturbances in brain development caused by addictive drugs. A useful survey is by Dan Lubman & Murat Yucel in the April 2006 issue, Of Substance. Consider:

Alcohol. Is a neurotoxin. It kills brain cells so alcoholics have smaller brains than light consumers of alcohol. Adolescents in particular are vulnerable to the effects of alcohol on memory-related brain functions. Research shows that the sizes of an adolescent's hippocampus and frontal brain lobes are significantly reduced by alcohol consumption.

And animal studies suggest that adolescent rodents can 'party harder' than older consumers without feeling sedated (this accords with high levels of 'binge drinking' among young people) while at the same time being subject to greater risk of disturbed brain development.

Nicotine. Animal experiments suggest nicotine is neurotoxic during adolescence though not during adulthood. Moreover, adverse effects on adolescents occurred even with much lower levels of exposure than typically consumed by regular smokers.

Cannabis. There has been much debate (including discussion here) about the links between cannabis use and psychopathology. This is a contentious area but again research is suggesting that, if there are adverse effects, these are most likely to be experienced at younger ages. Early onset cannabis use suggests increased risk of depression and psychosis. The explanation here emphasises links between genetic predisposition and cannabis exposure.

This is unsettled science and more research is needed. But there is the risk of a specific link between adolescent substance use and later psychopathology. While you can argue that young people should make up their own minds we know that, in youth, discount rates are high so agents are prone to impulsiveness. Thus, they can be better-off in terms of their own lifetime utility if early destructive impulses are curtailed. Indeed, as they age, these discount rates become lower. If risks are judged severe enough there are important implications for public health policy.