Locum tenens medical professionals work in different locations on an as-needed basis. Like a full-time psychologist, a locum tenens psychologist provides counseling services and mental health treatment to patients. Your duties can vary depending on the details of each temporary assignment. In most cases, you act as a fill-in psychologist and provide clinical services until the full-time mental health professional returns. You handle the caseload, make a mental health assessment of each new patient, and follow the existing plan for counseling or other treatment services for existing patients. Some locum tenens psychologists work in facilities that have a staffing shortage.