Substance abuse becomes substance dependence when the individual can no longer adequately function without the substance. At first substance abuse can serve to relieve pain and anxiety and sometimes depression. It can even bring pleasure. Eventually, however, these palliative results fade, and the abuser must consume the substance just so as to not to experience the withdrawal symptoms that occur when the central nervous system is deprived of the substance. Medically monitoring these withdrawal symptoms is unfortunately the major and often times only "therapeutic" focus for the typical drug rehab center. Monitoring withdrawal symptoms is the easiest part of the road to sobriety. Many addicts and alcoholics have been through this initial stage multiple times in one drug rehab center after another. These withdrawal symptoms inevitably become harder to manage the older the addict gets, even in the drug rehab centers where the staff are highly trained.