This video explores the complexities of substance addiction, explaining how addictive drugs affect the brain and why addiction is challenging to treat. It delves into the concepts of tolerance, dependence, and withdrawal, highlighting the impact on the brain's reward pathway and decision-making processes.

Substance Abuse Disorder As of 2021, more than 36 million people worldwide were estimated to be experiencing substance abuse disorder. This condition spans a spectrum of patterned drug use that causes issues in a person's life. At the more severe end of the spectrum is substance addiction. To understand why some people are more susceptible to addiction and why it can be so difficult to treat, let's take a look at how addictive drugs affect the body. When someone repeatedly uses an addictive substance, their brain may adjust to account for its regular presence. This is called tolerance. It diminishes the drug's effect and means more is required to produce the same experience. Alcohol, for instance, increases the transmission of chemical messengers like endorphins and GABA, which promote sensations of pleasure and calmness. When someone uses alcohol frequently, their brain will adapt to its presence. So when they don't use it, their brain receives fewer signals from those pleasure- and calm-inducing neurotransmitters, which impacts their energy and mood. In addition to the unique effects each addictive substance has, all of them alter the release of dopamine in a brain region called the nucleus accumbens. This area is part of the brain's reward pathway, which is sensitive to experiences that give us pleasure and drives us to repeatedly seek them out. The reward pathway is essential to our well-being, but addictive substances also exploit it. When someone is repeatedly using a substance and their body has adapted to its presence, they may develop dependence, where the drug is necessary for them to function comfortably. Meanwhile, repeated use can decrease the influence of the brain's cortex, which is responsible for driving deliberate decision-making and limiting impulsive behaviors. It can also increase the influence of the brain's subcortex, which is crucial in habit learning and impulsivity. Together, these changes can make someone feel a lack of control over how they're using a substance. This can mean suffering in other facets of their life and taking risks to continue using it. If the substance leaves their system, their body's equilibrium is disrupted, so they may experience cravings that motivate thoughts and behaviors of seeking and using the drug. And if they continue without the substance, they may experience withdrawal. Opioids, for example, relieve pain and induce sedation. Withdrawal from them causes heightened pain, anxiety, and insomnia. The faster a drug reaches the brain and stimulates the reward pathway, the more addictive it is.