Writing an essay about drugs, and then narrowing it down to the obsession is a good idea. You will have to narrow it down even more by providing three reasons people become addicted (obsessed). Most people report that they turn to drugs because they were upset and needed an escape...something to remove them from the pain of the situation for a while. Another reason people become addicted is because they start using them socially, to look cool or because they think it will enhance performance in some way. Lastly, people do drugs not intending to become addicted, like in the case of pain killers when they've had surgery, but in the end become dependent on the way it makes them feel.
