Relapse is the most painful and expensive feature of drug addiction -— even after addicted individuals have been drug-free for months or years, the likelihood of sliding back into the habit remains high. Though some relapse triggers can be consciously avoided, such as people, places and things related to drug use, other subconscious triggers related to the brain’s reward system may be impossible to avoid -— they can gain entry to the unconscious brain, setting the stage for relapse.