Is occupational therapy quackery?

No. Occupational therapy (OT) is a mainstream master's degree or doctoral level healthcare profession. Certified occupational therapy assistants have have a 2-year associate's degree.

The educational requirements at the professional level includes many of the same basic science and medical courses, using the same textbooks, as medical school.

The specific area of scientific study behind occupational therapy is occupational science, stemming from the profession's origins-the idea that, for humans, occupation is better than no occupation, or activity, beginning with WWI soldiers disabled by "shell shock" or physical disabilities, and moving into the large psychiatric hospitals of the day. The aides of the day began to see in practice that some activities were better than others, depending upon diagnosis, age, gender and other factors, and a body of knowledge began to develop.

Today, occupational therapists work with people in the entire age span from newborns to people at the end of life, and they work in the the many areas where life happens, home, employment, school, hospitals of many kinds, even prisons. Oh, and some OTs even specialize in driving and other ways to get between the places where life happens. So, if life isn't happening for you, you might need an occupational therapist.