Addiction (Substance Use Disorder) Psychologist

Psychologists hold a doctoral degree (PhD, PsyD or EdD) and are licensed by a state board. They provide talk therapy and are the only non-physician group generally licensed to administer and interpret psychological testing, such as assessments for ADHD, learning disorders or personality. In most states they cannot prescribe medication.

Substance use and addictive behaviour.

The formal definition

A psychologist with a proficiency that involves the application of psychological treatment of addiction stemming from the use of alcohol and other psychoactive substances (e.g., nicotine, marijuana, cocaine, heroin) or behavioral addictions (e.g., gambling) with the aim of cessation or reduction of use and/or the amelioration of emotional, behavioral, interpersonal and other problems arising from the addictive behavior.

Source: NUCC Health Care Provider Taxonomy code set. This is the definition used for billing and registration, which is why it reads the way it does.