It is a progressive mental disorder characterised as "a main, chronic disease of brain reward, motivation, memory, and related circuits" by the American Society of Addiction Medicine. It is characterised by a failure to manage behaviour, a dysfunctional emotional response, and an impact on the user's capacity to continuously abstain from the substance or behaviour." Addiction is defined in psychology as "a state that really can occur when a person takes a substance like alcohol, nicotine, or cocaine, or commits in an activity like gambling or shopping/spending. A person with an obsession takes a substance or engages in a lifestyle where the gratifying effects give a compelling reason to continue the activity despite the negative repercussions.