An Overview of

Drug Addiction

“Addiction” is a word often used in everyday language to describe different habits. It can have different meanings for different people; one person may say they are “addicted to cheesecake,” or “completely addicted to shopping.” Of course these statements are mostly exaggerated and do not generally refer to the disease addiction, a serious medical problem.

In medicine, there are several types of addiction including pathological gambling, compulsive disorders, and other addictive habits. However, when most physicians refer to the word “addiction” they usually mean “drug addiction” which is a recognized medical condition. Addiction as a science is a more complex concept than what we think it is and leaves many questions as to its long-term effects and understanding. This information is designed as an educational material specifically surrounding drug addiction.


Drug addiction is more than a bad habit; it is actually a disease of the brain, which is chronic and prone to relapse. According to the National Institute of Drug Abuse (NIDA) at the National Institutes of Health (NIH), “Drug Addiction” is defined as:

“A chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences.”

Experts commonly use the Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria for diagnosing/classifying drug addictive disorders. No matter what type of classifying method we choose to use, the diagnosis will always focus on the core elements of the definition.


As stated in the definition, drug addiction is characterized by compulsive behavior (drug seeking). This drug seeking occurs despite any harm that inevitably results. To the user, they will seek the drug despite any hurdles placed in their way.  In addition, the repetitive use of drugs can cause changes in the brain’s neurochemical architecture, which displays itself in the following symptoms:

  • Inability to feel pleasure in other healthy experience.
  • Previous pleasurable dose of the drug is not pleasurable anymore and hence, leads an addict to seek for a higher dose. This concept is called tolerance.
  • Seeking drugs to prevent painful experience of not having that drug in the system. This shift of drug seeking from pleasure to prevent painful experience becomes a significant distress to an addict.

The Neurobiology of Drug Addiction

The brain is a complex electrical-chemical organ.  Brain has 100 billion nerve cells called neurons that interact with each other through electrical and chemical signals. They talk with each other through these signals. The results of these electrical signals in specific brain regions give us the power to speak, imagine, feel, solve problems, and enjoy pleasure.

When one cell in the brain sends a message to another, it releases a brain chemical (neurotransmitters) that can be sensed by the second cell at a bind site (Neuro-receptor). This exchange of chemical information often occurs at tiny signaling junctions between cells called synapses.

The specific region of the brain responsible for pleasure and motivation is called the Limbic System. The most important brain chemical that is involved in the pleasure and motivation experience is dopamine, a naturally occurring brain chemical.  There are several behaviors, which can stimulate the Limbic System and act on dopamine. Anything that brings pleasure such as exercise, food, or sex, stimulates this area of the brain. This region of the brain is wired to remember what is pleasurable and create motivation to seek more. This, in fact, is the whole point of a reward system: to recognize and encourage “good things.” Addictive drugs cause excessive stimulation of the dopamine system, which gives intense euphoria.

Addictive Chemicals

Addictive chemicals are the chemicals that are responsible for causing the addiction. For example, ethanol in beer and spirits, nicotine in tobacco, tetrahydrocannabinod (THC) in marijuana and Opioids in heroin. 


National Institute of Drug Abuse (NIDA) reports that illicit drugs and alcohol cause more than 100,000 deaths every year in America. Tobacco use is the leading cause of premature deaths approximately half a million deaths every year in America alone.  Children are found to abuse drugs as early as 12 or 13; and it peaks at teenage.

How Drug Addiction Works

Addictive drugs act in the same brain region and alter the reward-related system. Drugs can mimic, or alter the dopamine in this region of the brain to heighten the pleasure senses.

There are three ways for an addictive drug to accomplish this:

  •  The drug can mimic dopamine and stimulate the receptors normally used by dopamine.
  •  The drug can encourage excessive release of dopamine in the system, leading to abnormally high levels of dopamine.
  •  The drug can interfere with normal recycling of dopamine, also leading to abnormally high levels of dopamine.

Therefore, the presence of an addictive drug can result in vast overstimulation of the “dopamine-based reward system” of the brain, a system that is wired to encourage repetitive use of the drug. This behavior helps us to understand some part of addiction.

Importance of Treatment

It is important to understand that drug addiction does not only affect brain and mental health but it also affects all other organs in the body. It can cause Cardiovascular disease, Stroke, Cancer, Hepatitis B and C, Lung disease and HIV/ AIDS. 


Drug addiction is a treatable illness.  Drug addiction can be well controlled by appropriate treatment programs. The treatment of drug addiction includes inpatient or outpatient treatment programs, counseling and self-help groups to help you resist using the addictive drug again. Thanks to the recent advances in neuroscience, we now have medications to help manage cravings as well as painful experiences from chronic drug use. 

The disease is chronic and is prone to relapse, meaning that it is not typically “cured.” It is important to understand that even if someone has stopped using drugs for many years, the individual is still at a risk of relapse at any time.

Risk Factors

Social, biological, and environmental factors interact with one another to trigger addiction. There are also genetic factors that influence the extent to which a person can be prone to addiction. If you have a blood relative with addictive illness, then you are at a higher risk of developing addiction. 


Fortunately, drug addiction is completely preventable. As long as you are not exposed to the drug, you will not get the disease related to the drug. However, there are times where we can be exposed to prescription drugs for therapeutic reasons such as narcotics for relieving pain and benzodiazepines for relieving anxiety or insomnia. In such cases, it is important to monitor the intake of these drugs closely in order to prevent addiction.

Having a healthy support system can help us avoid using drugs during stressful times like loss of a loved one, divorce, change of school and job loss.


  • Drugs, Brains, and Behavior The Science of Addiction  National Institute on Drug Abuse. – Accessed July 29, 2013.
  • Commonly Abused Drugs Chart  National Institute on Drug Abuse. – Accessed July 29, 2013.
  • Drug addiction – – Accessed July 29, 2013.