Addiction from the harmful dysfunction perspective: How there can be a mental disorder in a normal brain.

Is addiction a medical disorder, and if so, what kind of disorder is it? Addiction is considered a brain disease by NIDA, based on observed brain changes in addicts that are interpreted as brain damage. Critics argue that the brain changes result instead from normal neuroplasticity and learning in response to the intense rewards provided by addictive substances, thus addiction is not a disorder but rather a series of normal-range if problematic choices. Relying on the harmful dysfunction analysis of medical disorder to evaluate disorder versus nondisorder status, I argue that even if one accepts the critics' reinterpretation of NIDA's brain evidence and rejects the brain disease account, the critics' conclusion that addiction is not a medical disorder but is rather a matter of problematic nondisordered choice does not follow. This is because there is a further possible account of addiction, the evolutionary "hijack" view, that holds that addiction is due to the availability of substances and stimuli that were unavailable during human species evolution and that coopt certain brain areas concerned with human motivation, creating biologically undesigned peremptory desires. I argue that if the hijack theory is correct, then it opens up the possibility that addiction could be a true motivational medical disorder for which there is no underlying neurological-level dysfunction. Finally, I explore the implications of this account for how we see the social responsibility for addiction and how we attempt to control it.