A mental disorder with or without organic damage causes changes in personality, loss of contact with reality alteration in social functioning is called as Psychosis, the incidence, risk factors, Causes, Types and Clinical manifestations, Diagnosis and Treatment are explained. The Split Mind which causes a group of mental illnesses characterized by specific Psychological symptoms leading to disorganization of personality of an individual which interferes with thinking, emotions, behaviour and personality in total is Schizophrenia: Definitions, Classification, Aetiology, Psychopathology, Clinical Manifestations, Treatment, Nursing management, Sub types–Simple Schizophrenia, Hebephrenic/Disorganized Schizophrenia, Catatonic Schizophrenia–Catatonic Stupor, Catatonic Excitement, Residual Schizophrenia, Undifferentiated Schizophrenia, Post Schizophrenic depression, Acute Schizophrenic type, Latent Schizophrenia, Schizoaffective type, Childhood type of Schizophrenia, Paranoid Schizophrenia and Nursing Management are described in detail. Mood Disorders: Classification, Spectrum of illness, Aetiology, Psychodynamics, Treatment–Medical and Nursing Management. Depression–Types, Differences, Management, Involutional Melancholia are depicted in a detail. Mania–Aetiology, types–Hypo Mania, Dysphoric Mania/ Mixed Mood disorder, Circular type, Cyclothymia, Acute Mania, Delirious Mania and its Clinical manifestations., Treatment, Course of Prognosis and Nursing Management are explained in detail.