A
drug addict is a person who compulsively and conscienciously seeks and chooses the beneficial effects
reportedly provided by the recreational use of one or more
psychoactive substances (called the "desired effects", such as a sense of escape from reality and the individual's problems, mental stimulation, or even euphoria), despite being aware of the harmful effects and consequences said substance can cause to one's life and those of his loved ones.
"That guy from work keeps going to the bathroom
all day long to
snort blow. He's a full-fledged
drug addict!"