The prefrontal cortex is used for making all of your decisions. The neurons in your prefrontal cortex communicate with the neurons in the other places in your brain, playing a major role in weighing choices, controlling emotional responses and impulses, and making judgments. This region is already developed and connected to the rest of the rest of the brain when your an adult.
The prefrontal cortex of a teenager is not as effectively functional as an Adults. Neurons are partially covered with an insulation called a ‘myelin sheath’, which increases the speed of transmission of information. This padding can make the transmissions up to one hundred times faster! But the myelin sheaths in teenage neurons are still only half-baked.
Developing myelin sleaths begin at the back of the brain and slowly towards the more advanced parts at the front. The prefrontal cortex is the last to transform to this more advanced cerebral network. So while adults can make rational decisions quicker, teenagers are not as adept at doing so.
Most teenagers don't think things thoroughly when faced with emotional decisions. The researchers found that when processing emotions, adults have greater activity in their frontal lobes than do teenagers. The teenage brain isn't as controlled as adults. They don't fully have good judgement and are more prone to risk taking behavior.
90% of all addictions, such as alcohol and smoking, come from using the drug in their teenage years.