Addiction is a complex phenomenon that involves the brain's reward circuits. It's not limited to substances like drugs or alcohol, but can also extend to behaviors and even narratives or relationships. The addictive process, as discussed with Dr. Anna Lembke, is quite generalizable across different types of addiction, whether it's gambling, video games, sex, or work.
The nature of addiction also involves the dopamine system. As Dr. Robert Malenka pointed out, the rate of dopamine increase can be related to the addictive potential of a drug or behavior. Different substances and behaviors have varying degrees of addictive liability. For instance, substances like cocaine or opioids have a very high addictive liability, while others like caffeine, despite causing tolerance, may not have as high an addictive liability.
In essence, addiction is a continuum, and it's layered with complexity. It's about how substances or behaviors modify the reward circuitry and dopamine neurons in our brain.