Why Are Drugs So Addicting?: How Drug Addiction Affects the Brain

The brain is an almost incomprehensibly complex organ. Humanity is only beginning to scratch the surface of understanding how it is able to send and receive information, as well as monitor and control all of the voluntary and involuntary systems of the human body. It can help to think of the brain as an incredibly efficient organic computer; its neurons function sort of like binary processes, and it has an information storage limit (which could possibly be as high as 1,000 terabytes). Also like a computer, the brain relies on its ability to send and receive data to be able to function properly. For this to happen, certain chemicals are required.

Unfortunately, many of the chemicals in our brains are actually very similar to the chemicals that make up illegal drugs. Because of this, drugs can actually alter the way that information is passed within the brain. You see, when neurotransmitters encounter the chemicals in certain drugs (such as heroin or marijuana), they mistake them for naturally occurring chemicals, due to their similar structure. When the receptors attach to the harmful chemicals, the nerves are activated and begin to transmit incorrect messages. Some drugs (such as cocaine or methamphetamines) go a different route, causing nerve cells to produce an increased amount of neurotransmitters. This results in messages within the brain becoming heavily amplified, causing damage to natural information routes. The end result in either case is the release of a chemical called dopamine.

Dopamine is released by your body’s “reward circuit.” This circuit is responsible for the feelings of pleasure that you experience when you do something that is important for the welfare of the body. For example, a hungry individual will gain a burst of dopamine when he begins to eat, and sexual experiences release dopamine so that our species will be driven to procreate. In small doses at appropriate times, dopamine can be very useful—it forces us to acknowledge and remember important things, and helps create useful habits. However, drug uses causes dopamine to literally flood the brain. Some drugs can force the brain to release up to 10 times the amount of dopamine that would be rewarded for natural activities. Not only that, but the effects can be perceived much more quickly, and may last much longer. It is this reward that prompts users to continue to take the drug that is releasing such large amounts of dopamine into their system. Those who become addicted often receive such intense pleasure highs, that they stop pursuing natural sources of pleasure in favor of drugs.

Throughout all of this, the brain is still very active. We mentioned earlier that the brain is like a computer. That is true in some ways, but in other ways they are as dissimilar as night and day. For example, when the brain detects irregularities in itself, it can actually adapt to reestablish balance. As dopamine continues to saturate the brain, the brain compensates by reducing the amount of dopamine that it releases per experience. At the same time, the brain may reduce the number of signal receptors that can interact with the dopamine. As such, it becomes increasingly difficult for the drug user to experience pleasure. Non drug related activities that were once enjoyable will become uninteresting, and addicts may become depressed and listless. They will often increase their drug intake just to feel “normal” again, but as they do so, their brain will continue to try to adapt. As a user’s “tolerance” builds, larger and larger amount of the drug often become necessary just to stave off painful and dangerous withdrawal symptoms.

Other changes may occur in the brain as well. One such change involves the neurotransmitter glutamate. Glutamate is involved in the reward circuit, but it also assists in the learning process. As addiction takes hold, glutamate levels plummet, which can lead to a crippling impairment of cognitive functions.

Long term drug use will eventually cause changes and adaptations in other parts of the brain as well. Areas of the brain that affect judgement, decision making, behavior, and memory will all experience chemical imbalance, and can result in compulsive, strange, and dangerous behavior.

However, these changes need not be permanent. Given enough time, the brain can repair itself and the chemical levels can once again achieve a natural balance. For this to be possible, a user must be able to eliminate drugs from his system. This process takes time, but it can be done. Through drug rehabilitation programs, millions of addicts have been able to overcome their dangerous habits and find enjoyment and success in a drug-free lifestyle. But, despite the brain’s ability to heal itself, it will always retain the memory of the activities that were so pleasurable. As such, it will continue to try to drive the addict back into a relapse. This is why addiction is considered a chronic disease, and why drug relapse rates are so high.


For many users who enter rehabilitation, the process is long and difficult. Approximately half will relapse, and will need multiple rehabilitation attempts, but for those who succeed in regaining control of their lives, it’s worth all of the effort in the world. Online sites such as drugrehab.org can help addicts connect to a treatment program that is right for them.

The chemical balance in the human brain can easily be tipped through drug use, but with enough determination, an addict will be able to give himself time to repair.