Since there is so much variability among human beings, it is virtually impossible to universally define the precise stages involved in both addiction and recovery. In recent years, a number of prominent researchers have developed an important theoretical model aimed at describing addiction and recovery. This has coalesced into a "stages of change" model to explain the addiction process and its treatment. This model seeks to describe, as accurately as possible, the universal elements of addiction for all individuals who abuse substances. These stages exist on a spectrum, one end of which, for example, is the casual user of cocaine who realizes that his use is becoming a problem and quits without much difficulty. On the other end is the stereotypical "strung out" heroin addict who has lost job after job, alienated friends and family, and come close to death before seeking help and treatment. In the former case, even such "natural" quitters go through an evolution and a process of thought, perhaps mostly unconscious, before giving up the substance.