Psychiatrists and psychologists study the human mind. Either might provide psychotherapy -- a series of meetings in which patient and doctor discuss troubling feelings, thoughts and behaviors. However, distinct differences also exist between psychiatrists and psychologists.

Psychiatrists

Psychiatrists are physicians who specialize in mental illness. They attend college, medical school and residency, earn an M.D., and may also complete a two- to three-year period of specialized training called a fellowship. Psychiatrists must be licensed to practice in all states and are usually board-certified. They might specialize in addiction psychiatry, epilepsy, pain medicine, sleep medicine or other areas. As physicians, they understand the relationship between the body’s functions and mental illness. They are authorized to order diagnostic tests and lab work, prescribe medications and treatments, and hospitalize patients. The U.S. Bureau of Labor Statistics reports psychiatrists earned an average annual salary of $182,660 in 2013.

Psychologists

Psychologists study human behavior, thoughts, emotions and social interactions. Psychologists could specialize in clinical, counseling, school or industrial-organizational psychology. Most psychologists have a doctoral or specialty degree, but industrial-organizational psychologists might have a master's degree. Psychologists who practice independently or work directly with patients -- as opposed to performing research -- typically need a license. Board certification is not required for practice, but many psychologists are certified in fields such as clinical health, rehabilitation or neuropsychology. A clinical psychologist is the specialist most like a psychiatrist because both diagnose mental illness and perform psychotherapy, but psychologists cannot order lab and diagnostic tests or prescribe medications. Psychologists earned an average annual salary of $74,310 in 2013, according to the BLS.

2016 Salary Information for Psychologists

Psychologists earned a median annual salary of $75,710 in 2016, according to the U.S. Bureau of Labor Statistics. On the low end, psychologists earned a 25th percentile salary of $56,390, meaning 75 percent earned more than this amount. The 75th percentile salary is $97,780, meaning 25 percent earn more. In 2016, 166,600 people were employed in the U.S. as psychologists.