What are the implications of a world in which people can purchase a drug that allows them to live in a dream world?

For the sake of argument, assume this has been around for a while, and is thoroughly proven to be safe with no side effects. It is extremely cheap, and the only real issue is that it is highly addictive. <br><br>It's illegal in many countries, but the drug is mass produced and widely available in a consumable format.(Think of it squared like Theseus from Orphan Black). It's fair to say that a good 20% of the population of most western countries are using it. <br><br>What happens next?