Final answer:
Clinical psychologists are the professionals who must complete a supervised internship and obtain licensure to independently diagnose and treat mental disorders, distinguishing them from psychiatrists who can prescribe medication.
Step-by-step explanation:
The professionals who complete a supervised internship, and after board certification or licensure to practice, are qualified to independently diagnose and treat mental disorders are clinical psychologists. To become a licensed clinical or counseling psychologist, an individual typically needs to complete postdoctoral work under the supervision of a licensed psychologist, although this requirement has been waived by several states recently. Upon meeting state requirements and passing a licensure exam, they can work in private practice, hospitals, or other settings. While both clinical psychologists and psychiatrists can conduct therapy, clinical psychologists have a PhD or PsyD and can administer psychological tests, whereas psychiatrists, with an MD, can prescribe medications.