The basis for addiction
Scientists have long accepted that there is a biological basis for drug addiction, though the exact mechanisms responsible are only now being identified. It is believed that addictive substances create dependence in the user by changing the brain's reward functions, located in the mesolimbic dopamine system—the part of the brain that reinforces certain behaviors such as eating, sexual intercourse, exercise, and social interaction.
Addictive substances, through various means and to different degrees, cause the synapses of this system to flood with excessive amounts of dopamine, creating a brief rush of euphoria more commonly called a "high". Although the high may last only a few minutes, it also produces more longer-lasting effects in the brain. Dopamine signals occurring normally in the reward system (traveling from the ventral tegmental area to the nucleus accumbens) lead to the activation of proteins designed to calm the initial reaction and foster a continued desire to pursue the behavior responsible.
Addictive substances create a greater than normal dopamine release, and the subsequent reactions of the brain are greatly exaggerated as well. The amygdala, hippocampus, and frontal cortex associate the use of the drug with intense pleasure and well-being; an association that is strengthened with each exposure, and which over time comes to dominate normal thoughts and desires. When cravings for the drug are no longer controllable, the user is considered addicted. (For a contrary view of drug addiction, see Rat Park.)' Some in the medical field believe that what we call addiction is self medication for PTSD.
In addition Dr. Lonny Shavelson, in his book "Hooked," has reported that 70% of female heroin addicts were sexually abused as children. There also seems to be a genetic component to addiction. It is a little researched but well known secret in practicing medical circles that many addicts are self medicating for what we commonly call anxiety problems. PTSD is thought to be a common cause as is ADD/ADHD, and bipolar disorder. Some research is being done on the subject, more needs to be done.
