The answer is all of the above. This is so because any illegal drug is addicting because if the stimulants that effect your brain, and because of how they make the person feel... AKA they get high... Also, the person who takes the drug begins to "need" it to feel normal or better. this is called withdraw effects when the person has gone so long without taking an injection or something, then they start to become disorientated and feel bad until they take the drug again. this is part of the addiction. At first though, the person takes the drug and does not feel negative effects, so they most likely "sense" that it is OK to continue taking the drug despite known facts. Then after the short time, they do actually become fully addicted. But despite this, the addiction is usually most immediate.
