The clinical definition of drug addiction is:
“Drug addiction is a chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences. It is considered a brain disease because drugs change the brain – they change its structure and how it works. These brain changes can be long lasting, and can lead to the harmful behaviors seen in people who abuse drugs.”
Anyone who uses drugs has the potential to become a drug addict. Addiction typically does not happen overnight. When, where, and how a person becomes a drug addict depends on many different factors like, what drug is taken, the amount being taken, and the person’s history, including background, genetics, and current social situation. However, no matter what, if you are taking a drug, there is the possibility that you could become addicted to the substance.1
Addiction happens because the chemicals in a drug connect to the areas in your brain that control when to feel happy, when to feel sad, when to feel pain or when not to feel pain.
When you take a drug, chemicals from the drug dissolve you’re your blood, go to your brain, and causes an abnormal release of pleasure giving chemical (dopamine). This floods the part of your brain that controls pleasure and pain with dopamine, giving users that euphoric rush.
Normally, your body releases dopamine when you do activities like eating good food, exercising, having sex, doing something rewarding, etc. When you take drugs, the drug causes dopamine to be released in your brain and, for a certain period of time, actually blocks the brain’s ability to recycle dopamine in the place where it came from. Essentially, this blocks your brains ability to stop feeling high. This makes dopamine stay in your brain longer and causes you to have pleasure for a certain period of time. This may be one reason why different drugs have different lengths of keeping you high. When taking heroin, the high lasts a couple of hours. Cocaine is 10 to 30 minutes. Meth lasts for several hours. Other drugs are shorter or longer. For more information about this process, check out PBS’s Frontline piece on meth.2
The brain likes this rush of dopamine that make you feel good. So, it sends signals that cause you to want that high again, causing you to take drugs a second, third, fourth time. Psychologically, you want to get back to that place of feeling good. This is one thing that drives you to continually use drugs and become addicted.
Secondly, when you take a drug it does three things to your brain:
1) floods your brain with an unnatural amount of dopamine,
2) blocks the pathways in the brain to release the drug and
3) extends the stay of dopamine in your brain.
What this does to your brain biologically is that the drug eventually destroys your brain’s ability to make its own naturally occurring chemicals to make you feel good.
The drug depletes dopamine in your body, so that you cannot create it as fast as you did before you to took drugs. It also over stimulates the transmitters that send and receive the dopamine in your brain, eventually destroying them. Because the drugs have changed this part of how your brain functions, if you are a drug abuser you will not feel as happy as you have before when you are not on drugs and have really good food, sex, or doing something that should give you positive and happy feelings.3
Therefore, when an addict goes through detox and begins recovery, they may be sad, depressed, irritable, etc. for awhile because his/her brain has been altered by the drug so it cannot produce dopamine on its own. There are many studies being conducted about whether or not, once off drugs, the brain can recover and produce dopamine by itself again. In the meantime, this is one of the contributors to why addicts relapses; they feel like cannot be happy without drugs, and they don’t want to be depressed, so they use again.
The UCLA Integrated Substance Abuse Programs (ISAP) and Eyes of the World Media Group have developed a video series that explains this process. This curriculum focuses on meth use, but the same general principles and processes apply for most other drug use. The Hawaii Meth Project has a link to this curriculum that explains the process.