Biological changes in the brain can also lead to addictions. The dopamine pleasure circuit is not the only part of the brain involved in addictions. The prefrontal cortex located in the frontal lobe of the brain can also be affected. The prefrontal cortex is involved in our ability to make logical, rational, and appropriate decisions.
In a non-addicted individual, the dopamine pleasure circuit is in balance with our prefrontal cortex. If a person experiences the euphoric feeling of cocaine, the dopamine pleasure circuit would be in favor of pursuing that activity. The prefrontal cortex would balance this urge by helping the person think through the subsequent consequences of using an illegal drug.
However, when the usual balance between the dopamine pleasure circuit and the prefrontal cortex is disrupted by the introduction of excessive amounts of dopamine, the potential to develop an addiction has occurred. The dopamine pleasure circuit wins out and the addicted individual experiences a decreased capacity to make healthy choices related to addictive substances or behaviors.
What often happens is that a person will use a potentially addictive substance out of curiosity or a desire to experiment. Once the dopamine pleasure circuit is activated by the substance of abuse, the body's natural reward/pleasure pathways are disrupted.
Because drugs of abuse are often capable of releasing two to 10 times more dopamine than the body's natural system, a more powerful reward system is artificially developed. The person's brain system becomes altered and there is a hunger for more of the addictive substance to obtain feelings of pleasure. An addiction is born.
Why do adolescents seem particularly prone to developing addictions?
The prefrontal cortex is the last part of the brain to develop, and so the immature brains of children and adolescents are less able to manage both the decisions involved in starting addictions and the ability to chemically handle addictions. Therefore, once an addictive substance is introduced into the adolescent's brain, the dopamine pleasure circuit tends to dominate decision-making.