In the last 20 years, research on substance addictions has changed its focus from the social foundations to the neurobiological foundations. Hence, some behaviors have begun to be considered as equivalent to addiction based on proposed criteria: salience, withdrawal symptoms, tolerance, conflicts, relapse, and mood modifications.

New knowledge about the brain's reward system suggests that “as far as the brain is concerned a reward is a reward, regardless of whether it comes from a chemical stimulus or an experience.”

Pathological gambling was the prototypical addiction disorder, sharing some hallmarks with substance addictions: a high rate of comorbidity and treatment response to pharmacotherapies, such as opioid antagonist. However, compulsive sexual behavior, compulsive exercise, food starving, binge eating, and, most recently, Internet addiction have been gradually conceptualized as non-substance addictions with overlapping features with substance dependence. Several definitions” have been adopted regarding these behaviors: natural addiction, non-chemical addiction, and negative dependence are only some examples. This issue of CNS Spectrums focuses on behavioral addictions.