In a person who becomes addicted, brain receptors are overwhelmed by the influx of chemicals from substances like stimulants, nicotine, opioids, alcohol and sedatives. This causes the brain to respond by producing less dopamine or eliminating dopamine receptors, an adaptation similar to lowering the volume of a speaker when the noise becomes too loud. This makes a person's brain believe that these substances are essential for survival, more essential than food, shelter or even relationships. Addiction affects the brain on many levels.
Once a chemical enters the brain, it can cause people to lose control of their impulses or want to consume a harmful substance. These changes don't go away quickly and the biological memories of the drug can be as deep and lasting as any other type of memory, and the signals can trigger the executive system to start the drug search years after the most recent previous exposure. So addiction is much more than just seeking pleasure by choice. Nor is it just the unwillingness to avoid withdrawal symptoms.
It is a hijacking of the brain circuits that control behavior, so that the behavior of the addict is totally directed to the search and use of drugs. With repeated drug use, the reward system of the brain becomes subordinate to the need for the drug. There have been brain changes that are likely to influence the addict for life, regardless of whether or not they continue to use the drug. The search for the superplacer consumes everything. What starts out as a casual habit can quickly degrade into addiction due to the brain mechanisms involved.
At first exposure, the brain receives a shock of 20 mg of dopamine into the system. This surge of feel-good chemicals in the brain is much more than what can be achieved with real-life experience. Therefore, with this large dose of dopamine, the brain remembers the experience and wants to come back for more. The brain, being the most sophisticated thing in the world, tries to calibrate itself back to normal.
By doing so, it makes you need to consume more to get the same high - more alcohol, more drugs or more pornography. Grab your sleigh, 'cause here comes the slope. Scientists now think that brain changes associated with genuine addiction last much longer than the withdrawal phase of any drug. The addict will also have to relearn impulse control; his executive system will have to be retrained to inhibit impulses toward drug use as they occur. Some scientists have proposed that addiction hijacks normal reward circuits and, therefore, disrupts the normally perfectly quantifiable relationships between reward and behavior. The most important contribution that anyone who deals with addicts can make is to recognize that reversing addiction is not just a matter of giving up something pleasant, but of accepting that addicted people have undergone a formidable reorganization of their brains.
People have been using addictive substances for centuries, but only very recently, by using powerful tools such as brain imaging, genetics and genomics, scientists have begun to understand in detail how the brain becomes addicted. Acute abstinence is one of the first problems faced by any addict after they stop using drugs and this process plays an important role in maintaining drug use behavior. Some addictive drugs such as nicotine may seem quite harmless because they don't produce a deep “buzz” or euphoria. As the brain adjusts to normal an addict may gradually decrease their substitute drug until they become drug-free. Drugs can alter important areas of the brain that are necessary for life-sustaining functions and can boost compulsive drug use that marks addiction.
Addiction is characterized by a deep desire for a drug (or behavior) that dominates an addict's life so much that practically nothing can prevent them from engaging in addictive activity. We must adopt same attitude towards addictive diseases and offer extensive and intensive treatments. Until recently researchers were patiently focusing on individual molecules one at a time to assess their possible role in addiction.