Mental disorder refers to a variety of illnesses that influence mood, thinking, and behavior. A symptom of a mental disorder represents a specific functional disturbance (e.g., hearing voices in the absence of external stimuli, a psychotic symptom). A syndrome comprises a cluster of symptoms that tend to co-occur (e.g., lack of insight, disturbances in perception, and disorganized thoughts and speech are some of the individual symptoms that form the syndrome of psychosis). A disorder is a specific syndrome with a specific temporal course (e.g., at least two of five specific symptoms need to be present for 1 month to diagnose schizophrenia according to one diagnostic system). Although many people experience mental health problems at some point during the course of their life, such problems are ...