What is the hardest addiction to quit?

Depends: Some substances are inherently more addictive, like heroin and nicotine. But it really depends on the individual. Ex someone may be addicted to both Cocaine and marijuana, they may give up the Cocaine but have much more difficulty with the marijuana. Or they give up alcohol and the cigarettes still hold a powerful grip. I would say the last addictive substance is the most difficult, but can be don.

It Depends: It's the one that most affects a given person. For the person, the substance they are addicted to, that is the one hardest to give up, or else they wouldn't have an addiction to it. The most widely used drug in the world is caffeine. Nicotine and alcohol cause the greatest impact world wide. A recent study says every single cigarette smoked costs society seven dollars in medical costs, etc.

Cigarettes are hard.: Opioids kill via overdose, alcohol destroys lives, families, and livers. While narcotics seem the most deadly, the use of buprenorphine and inhouse rehabs works. There isn't any consistent treatment for tobacco addiction, although many methods are used.