Treatment resistance refers to the phenomenon where a patient does not respond initially or stops responding to a particular treatment or medication. This can occur in various medical conditions, such as cancer, depression, and schizophrenia. Treatment resistance can be caused by a variety of factors, including genetic factors, environmental influences, and the development of mutations or changes in the disease itself. Researchers are studying treatment resistance in order to develop new and more effective treatments, as well as to identify ways to predict and prevent resistance from occurring in the first place.