An example of a heroin abuser responding to a placebo would be a(n)

Needle freak  
A person who is used to abusing durings by injecting substances in his body can be easily deceived into feeling that an empty needle will make him get same response this is because of the expectation that the needle will make him high as his mind have already been conditioned to the fact that a needle injected into his body will make him feel certain effects.