As a nation, we are drinking much more than we used to, which is partly attributable to alcohol being cheaper and more available than ever. Many British teenagers get into the habit early, although recent trends  suggest this situation is improving (alcohol consumption among teenagers is slightly lower than it was ten years ago).
Nonetheless, drinking alcohol during adolescence is not a good idea, because the younger you are when you have your first alcoholic drink, the more likely you are to develop problems later on in life . The same is true for cigarette smoking and the use of illicit drugs such as cannabis and cocaine.
Why are adolescents particularly vulnerable to addiction? A large part of the answer comes from our understanding of the neurobiology of brain development during adolescence. The brain does not reach maturity until fairly late in life, with new connections between brain cells being formed right up until people are in their mid-20s .
Importantly, the brain does not mature at a uniform rate. The more primitive regions of the brain, including the reward system and other areas of the subcortex such as those parts that process emotions, reach maturity relatively early (when people are in their early teens).
The more “advanced” parts of the brain, such as the prefrontal cortex, are not fully developed until much later. In behavioural terms this means adolescents are particularly sensitive to their emotions and to things that are novel and motivationally appealing, but they are relatively unable to control their behaviour and plan for the future.
My research  suggests this can explain why some adolescents drink more than others: teenagers who were relatively poor at exerting self-control, or who took more risks on a computer test of risk-taking, were more likely to drink heavily in the future.
This creates perfect conditions for vulnerability to addiction during adolescence, because the motivational “pull” of alcohol and other drugs is very strong, whereas the ability to control behaviour is relatively weak. Many scientists think if adolescents do drink a lot, and if they do it frequently, then this might cause long-lasting changes in the way that the brain is organised, which can make it very difficult to stop drinking.
We certainly see changes in the brains of people with alcohol problems (compared to people without problems), but it can be difficult to work out if alcohol caused those brain changes, or if those people had slightly different brains before they started drinking, and these subtle differences may have led them to start drinking in the first place.
Addiction and behaviour
In principle, adolescent brains could be vulnerable to “behavioural” addictions as well as alcohol and drug addiction, for exactly the same reason. Very few behavioural addictions are officially recognised by psychiatrists and psychologists at the moment (gambling addiction is the only exception).
The Channel 4 documentary Porn on the Brain  shown this week asked whether pornography is addictive, and if adolescents could be getting hooked. As shown in the programme, it certainly seems to be the case that a minority of adolescents who use pornography exhibit some of the characteristic features of addiction, such as feeling unable to control their use of porn, and loss of interest in other activities.
Their patterns of brain activity when viewing porn seem to be similar to those seen in people with alcohol and drug addictions when they look at pictures of alcohol and other drugs. It remains to be seen whether addiction to porn will eventually be recognised as a psychological disorder, but it is clear that it can create problems for some adolescents and young adults who use it.
What can be done? Although it’s obvious, parents should do what they can to prevent their children from experimenting with alcohol, smoking and other drugs for as long as possible. The same applies to other things that might eventually be considered “addictive”. School-based prevention programmes can also be successful, including a recent program that is tailored to different personality types and has shown some promise  at reducing alcohol consumption in teenagers.
Hard Evidence  is a series of articles in which academics use research evidence to tackle the trickiest public policy questions.
Matt Field receives funding from the Medical Research Council, Economic and Social Research Council, Wellcome Trust, British Academy and Alcohol Research UK. He is affiliated with the UK Centre for Tobacco and Alcohol Studies.