Ever wondered why teenagers take more risks and are more prone to addiction? It's because their brains respond differently to a situation than adults, says a new study.

In experiments on mice, researchers at the University of Pittsburgh have pinpointed some differences in brain response to a food reward between adolescent and adult rodents.
The findings, published in the journal Proceedings of the National Academies of Sciences, could explain why adolescents take more risks and are more prone to addiction, depression and schizophrenia, the researchers said.

"The brain region that is very critical in planning your actions and in habit formation is directly tapped by reward in adolescents, which means the reward could have a stronger influence in their decision-making, in what they do next, as well as forming habits in adolescents," study researcher Bita Moghaddam told LiveScience.

"Teens could do stupid things in response to a situation not because they are stupid, but because their brains are working differently. Somehow they perceive and react to a situation differently," Moghaddam said.

The study was performed in rats, but teenagers throughout the animal kingdom show the same risk-taking and impulsive behaviours as human teens, so the results are likely to be applicable in humans too, the researchers said.

Other studies have shown that the teen brain is also more susceptible to stress than the adult brain. Teenage brains are especially susceptible to addiction and mental illness, and the differences in the brain at that time may play a big role in these diseases. "If your brain is processing the exact same thing differently, that could give us clues as to why their brain is more vulnerable," Moghaddam said. "By understanding what is happening in the brains of adolescents we can better understand how to prevent disease."

The nucleus accumbens is the part of the brain that reacts with happy "reward" chemicals when we eat, have sex or do other things that ensure our survival. Drugs activate this region as well, creating an artificial reward signal by making these neurons send out their feel-good chemicals.

The researchers saw very similar reward responses in the nucleus accumbens when the rats received food pellets; the big difference between the brains of teenage and adult rats occurred in the dorsal striatum, where more activity showed up for teen rats about to get a food pellet.

This brain region gets activated by the reward signals from the nucleus accumbens and is involved in habit formation, sort of sealing in the memory of "I put my nose in here and I get a treat that makes me feel good."

These brain differences could manifest as the impulsive and risk-taking habits of your average teen, Moghaddam said.

"It could make the adolescent brain more vulnerable to what goes on around them in the environment, to things that are expected to be rewarding, and could make the brain more vulnerable to addiction," she said.