Hard Evidence: Is the teenage brain wired for addiction?

The younger you are when you have your first alcoholic drink, the more likely you are to develop problems later on in life.

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.

Rates of teenage drinking are dropping. NatCen

 

Arrested development

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 prefrontal cortex is a late bloomer. National Institute of Health

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.

Taking risks

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.

Starting early carries greater risk. NatCen

 

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.

This article was originally published at The Conversation. Read the original article.

Teenages making a toast in a pub. Photo: Getty

Matt Field is Professor of Experimental Addiction Research at the University of Liverpool.

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How the Night Tube could give London’s mice that Friday feeling

London Underground’s smaller inhabitants might be affected by the off-squeak service – and learn when the weekend’s coming up.

What will the mice who live in the Tube network make of the new all-night service? Half a million of them are thought to have made the London Underground their home – and will be in for a surprise when the Victoria and Central lines keep running this weekend.

The Londonist is concerned the mice “are unlikely to get any sleep” with the new Night Tube, and may move to the District line instead. Yet a number of scientists point out to the New Statesman that mice are nocturnal creatures, most likely to sleep while the lights are on and the trains are running.

So will they get on board with the change – or make a run for different platforms on other lines?

The bad news:

“When the Tube’s away, the mice will play,” is how the rhyme (almost) goes. 

Many have come to know  and even love  the mischiefs of the mice who stream off the tracks and out of the tunnels as the stations close at night, in search of discarded morsels of Maccy D. And until now, they’ve had a good few hours to conduct such galavanting in peace. But the new system means they will have to re-structure their sleep and foraging cycles, or “circadian rhythms”. 

“The presence of night trains should upset several of these entrainment factors (or zeitgebers = time givers) leading to disturbances in their behaviours,” explains Professor Patrick Nolan, from MRC Harwell, an international centre for mouse genetics. 

“When you fly across the Atlantic, for example, it takes a few days to adapt, you feel a bit groggy, don't perform as well as you usually do, don't eat well, etc. You soon adapt to the change. But if there are constant disruptions like this, the effect may be more severe and long-lasting. And this is how the schedule changes in the Underground might affect the resident mice.” 

So it's the constant switching between the week and weekend schedules that could leave the mice  and Tube drivers  most cheesed off. Agoraphobia (fear of open spaces) and photophobia (sensitivity to light) are two possible effects of the resulting anxiety, and their mating patterns and liver functions are also likely to be disturbed.

The good news:

Yet it is unlikely mice will be leaving the Night Tubes for good. 

The more time we humans have to drop our dinners, the larger the menu becomes for the mice (researchers tell me that strawberry milk and Wheetos are particularly favoured fare).

“Mice are active most of the time – so more trains at night hours will not make such a difference to them,” say the RSPCA’s wildlife officers. “In fact, it may help as it may provide more foraging opportunities.”

They’ve also faced worse before. The London Transport Museum reminds us that, during the Second World War, cats were employed to counter vermin on the network (spot the cat in the 1940s TfL workers' canteen below).


Credit: London Transport Museum

For Dr Samuel Solomon at UCL, there is plenty to suggest the mice will successfully adapt. His study of mouse reflexes shows how they respond to various visual stimuli – and can start running within one-tenth of a second. “There might be cues they pick up – if people clean the station differently on Fridays, for instance.”

The tracks’ electric current may no longer be entirely switched off (if it ever was), but their whiskers’ sensitivity to vibrations could help them juggle their escapades to fit around the Night Tube’s less frequent service.

What Dr Soloman can’t yet predict is whether the mice will start to anticipate that Friday feeling: “It will be interesting to see whether they can learn that Friday is Friday”.

All in all, the Tube mice seem well set for the Night Tube’s new challenge. Who knows, they may soon gain the confidence of their 24/7 brothers in New York – and start ordering take-out...

India Bourke is the New Statesman's editorial assistant.