This document discusses several psychological conditions that can be featured in psychological thrillers: depression, schizophrenia, and bipolar disorder. It provides details on the symptoms, treatments, and course of each condition. Depression symptoms include feelings of sadness, hopelessness, and loss of interest. Schizophrenia symptoms include hallucinations, delusions, and disordered thoughts. Bipolar disorder involves alternating periods of depression and mania, with a wide range of associated symptoms for each state. Treatments involve medication and therapy.