Why teenage brains are so different

THE brain takes a long time to form completely. The wiring in a teenager’s brain is only about 80 per cent completed (which may not come as a great surprise to their parents).

Although most of the growth of the brain occurs in the first two years and is 95 per cent finished by the age of ten, the synapses – the tiny spaces between nerve cell endings – aren’t fully wired until a young person is in his or her mid to late 20s. That means that the teenage years effectively extend well into adulthood.

In the meantime, the person in question will almost certainly have more impulsive, less reflective behaviour than his elders, and will also be more susceptible to the effects of alcohol. ‘The teenage brain is not just an adult brain with fewer miles on it,’ Frances E. Jensen, a neurology professor, told Harvard Magazine in 2008. It is, rather, a different kind of brain altogether.

The nucleus accumbens, a region of the forebrain associated with pleasure, grows to its largest size in one’s teenage years. At the same time, the body produces more dopamine, the neurotransmitter that conveys pleasure, than it ever will again. That is why the sensations you feel as a teenager are more intense than at any other time of life. But it also means that seeking pleasure is an occupational hazard for teenagers. The leading cause of deaths among teenagers is accidents – and the leading cause of accidents is simply being with other teenagers. When more than one teenager is in a car, for instance, the risk of an accident multiplies by 400 per cent.