Addiction is a complex phenomenon that has been studied for decades, yet its underlying mechanisms remain largely unknown. Science has made great strides in understanding the way the brain changes in addiction, and the effects of drugs and alcohol on neurotransmitters and neural pathways. At its core, addiction is a brain disorder that alters the way the brain functions. When drugs and alcohol are introduced, they disrupt the brain's natural balance.
In response, the brain adapts to the presence of these substances, leading to changes in both its structure and functioning. For instance, when a drug artificially recreates the effects of dopamine, the brain reduces its own production of this neurotransmitter. This can lead to an imbalance in the brain's chemistry, which can be corrected by taking more of the drug. Over time, this cycle of drug use and adaptation can lead to substance use disorder (SUD).
The effects of different substances on the brain vary slightly, but all addictive drugs - including alcohol, opioids, and cocaine - produce a surge of dopamine in a region of the brain called the basal ganglia. This dopamine surge is what creates the feeling of pleasure associated with drug use. At the same time, this dopamine surge can lead to conditioned learning - meaning that people who develop an addiction are at risk of relapse even after years of abstinence. This is because exposure to drug-related cues can trigger an automatic response to take more drugs.
Addictive drugs also affect another part of the brain called the nucleus accumbens. This region is associated with habit learning and is responsible for keeping individuals in a cycle of ups and downs as they take more drugs to correct an imbalance in their brain chemistry. Research has also shown that glutamate receptors in the nucleus accumbens are altered when addicted rats no longer receive drugs and eventually give up their search for them. Glutamate is a neurotransmitter that plays an important role in learning and memory, so it makes sense that it would be involved in addiction. The cost of illicit drug addiction in the United States is estimated to be more than $600 billion per year, with profound social and economic impacts. It is clear that addiction is a serious problem that needs to be addressed. Fortunately, science has come a long way in helping us understand addiction and its effects on the brain.
By continuing to study how drugs affect neurotransmitters and neural pathways, we can gain insight into how addiction works and develop better treatments for those struggling with substance use disorder.