The Science of Addiction

   Drug addiction may start with an “It’s just once.” A fleeting thought, an impulse. Then it may turn into “one more time,” and continue with an almost uncontrollable compulsion. It may also start with being prescribed pain medication and becoming dependent. What happens between taking a drug once and relentless need? How does addiction take over? Some people have a predisposition to addiction, whether because of genetics or environment, but once taken repeatedly, drugs alter the brain’s sensitivity to dopamine and make one dependent on using drugs to feel pleasure, according to Surgeon General ( According to the National Center for Biotechnology Information (NCBI), this, among other adaptations in different parts of the brain, is what contributes to the continuation of this harmful cycle: intoxication, withdrawal, and craving (

   According to Biomedical Teacher Leslie Wymer, the network of chemical and electrical signals relayed between neurons by neurotransmitters is what allows one to sense and understand their own environment. This network also allows movement in response to the sensation of the environment. An example of this is pulling back your hand (movement in response) when it touches a hot stovetop (sensing the environment). Neurons and neurotransmitters facilitate this. In the brain, the process allows us to experience emotion. In relation to addiction, the reward circuit of the brain plays a major role. According to the NCBI, this system “…has been recognized for its central role in motivated behaviors, various types of reward, and, more recently, in cognitive processes.” It is able to activate a state of seeking in an organism, which encourages organisms to search for things that support life and avoid harmful things, to essentially ensure survival. Dopamine, a neurotransmitter involved with “…the orchestration of goal-directed behaviors, and in the promotion and reinforcement of learning” is the chemical most associated with the reinforcement of the effects of drug addiction (

   Different drugs have different effects on the nervous system, but all drugs have one common consequence: they create a tolerance towards dopamine. This characterizes the craving and “chasing a high” part of the addiction cycle. According to the National Institute on Drug Abuse (NIDA), some drugs produce a surge of dopamine, much more than what is naturally produced (nida. Because of this, the reward circuit acclimates to the new levels of dopamine. This adjustment means users would need more and more of the substance to feel pleasure, and in later stages of addiction, to feel “normal.” This contributes to the development and maintenance of addiction.

   Activities that would normally bring someone pleasure, like eating or social interaction, would not evoke the same feeling they did before drug use because of the dopamine tolerance. This can have unintended consequences. According to the Surgeon General, because the reward circuit isdisruptedbydruguse,lifecanfeeldulland less enjoyable when users aren’t using the drug. The association of surroundings with the feeling of pleasure caused by substance use is also a consequence (addiction. If a substance is used repeatedly in the same place or with the same people, being in that place or around those people can be associated with the high caused by the substance use. This maintains the cycle of addiction.

   Addiction has both positive reinforcement (the high when using a substance and the desire to feel that high again) and negative reinforcement (withdrawal or “escaping a low”), with positive most common in earlier stages of addiction and both positive and negative reinforcement in later stages. Other parts of the brain contribute to the continuation of the addiction cycle through negative reinforcement. Disruptions in the prefrontal cortex because of addiction “reduce functioning of brain executive control systems, which are involved in the ability to make decisions and regulate one’s actions, emotions, and impulses,” according to the NCBI ( According to the NIDA, “The extended amygdala plays a role in stressful feelings like anxiety, irritability, and unease, which characterize withdrawal after the drug high fades and thus motivates the person to seek the drug again” ( The impaired functioning of the decision making part of the brain and the role of the motivator to escape withdrawal work together to make up the craving and withdrawal factors of addiction respectively. These factors maintain the cycle of addiction.

The addiction cycle can be broken with dedication, but this dependence is dangerous and life-changing. No one chooses to get addicted, but it can happen to anyone.