Ahas usually had four years of graduate school and one or more supervised internships; a is a medical doctor who has completed a one-year internship and a three-year supervised residency in the biological and therapeutic treatment of mental disorders.

psychologist; psychiatrist        

Explanation:

                A psychologist is a person who treats a person an diagnose persons who are suffering from any mental illness or mental stress.  They specially focus on psychotherapy and treat mental and emotional distress. To become a psychologist, a person needs to have one or more internship under an expert after he or she have completed her four year graduate course in psychology from an university.

               On the other hand, psychiatrist is a person who can prescribe medicine tot eh patient who is suffering from any mental disorder. Psychiatrist is a trained medical practitioner or doctor. A psychiatrist generally spends most of the time with their patient analyzing and diagnosing the patients problems.

               To become a psychiatrist, a person after becoming a medical doctor needs to have one year medical internship and then undergo a  three-year or four-year residency training. At this training, they specialized in psychiatry and learn about the treatment and diagnosis  modalities for each and every psychological condition.

Thus the answer is --

psychologist; psychiatrist  

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