Addictive drugs were found to lower the threshold of self-stimulation in more detailed analysis. Wightman's studies on dopamine transporter knockout mice and self-stimulation effects on stimulated dopamine release do not agree with this concept. Attention is important in addiction, and as a component of recognition of reward or punishment. Koob's studies focus more on addiction and the balance between pleasure associated with positive reinforcement and responses to positive or negative affective states that lead to conditioned responses, or habits. Addiction may be a process driven by drug-induced changes in affect, driving adaptive behavioral responses in an effort to maintain homeostasis, e.g., normal healthy states.
Drug abuse alters the normal state in two ways.
The positive affective state of reward is reduced and the negative affective state of withdrawal is enhanced. These factors combine to promote additional drug taking behavior. Koob has shown that a history of drug consumption leads to increased drug consumption for alcohol, cocaine and opiates. Although the physical signs of alcohol withdrawal are over in about a week, an extended withdrawal of much longer time leads to an increased drive to drink in experienced animals. This is consistent with AA literature suggesting that recovered alcoholics are always at risk of a rapid return to alcoholism if they return to drinking.