There is no straightforward answer to the question of which drug is most addictive. The subject of addiction in general does not come in black-and-white terms. There’s a lot of gray area when it comes to figuring out if a person has an addiction disorder, and the very definition of the word addiction leaves a lot of room for interpretation.
Most addiction experts agree that there’s both a physical and a psychological aspect to addiction. Addictive substances have physical effects on the brain and cause pleasurable sensations that prime the brain’s pleasure-reward response. At the same time, a person’s stress levels, life satisfaction, attitudes about drug use, and the presence of other mental illnesses are all considered to be factors in the development of an addiction disorder. People can even become addicted to substances that are not considered to be physically addictive because they can form an emotional attachment to the drug and any kind of intoxicant will cause the brain to associate that drug with a pleasure reward.