Finally, nausea may be psychological in origin (which is not to say that it is less severe or significant or any less real)
. Doctors have recognized a specific nausea of this type, which they call anticipatory nausea and vomiting. It usually occurs in patients who have had nausea after chemotherapy, who then go on to become nauseated at the next session, even before treatment is started. This reflex may be so strong that simply driving by the hospital or seeing one's nurse at the supermarket can trigger an episode of nausea and vomiting.