In Brave New World, most of the World State members are happy, but this is very artificial. The members of the World State may be happy on the surface, but their lives have no meaning. They feel no deep emotions like love and hate. They take soma, a drug that makes them happy, to escape from their true feelings, which may upset the stability of the society. Everything in the society is based on giving people instant gratification to keep them content for the moment so that they won't question anything or discover the truth about themselves or the world.
The use of ecstasy today is a lot like the use of soma in the World State. People use to escape from bad things in their lives so that they can feel happy. This happiness is very artificial, though, and people's real feelings will still be there when they are no longer high.