Psychoses, Substance-Induced: Psychotic organic mental disorders resulting from the toxic effect of drugs and chemicals or other harmful substance.Hallucinations: Subjectively experienced sensations in the absence of an appropriate stimulus, but which are regarded by the individual as real. They may be of organic origin or associated with MENTAL DISORDERS.Diagnosis, Dual (Psychiatry): The co-existence of a substance abuse disorder with a psychiatric disorder. The diagnostic principle is based on the fact that it has been found often that chemically dependent patients also have psychiatric problems of various degrees of severity.Psychotic Disorders: Disorders in which there is a loss of ego boundaries or a gross impairment in reality testing with delusions or prominent hallucinations. (From DSM-IV, 1994)Emergency Services, Psychiatric: Organized services to provide immediate psychiatric care to patients with acute psychological disturbances.Substance-Related Disorders: Disorders related to substance abuse.Delusions: A false belief regarding the self or persons or objects outside the self that persists despite the facts, and is not considered tenable by one's associates.Schizophrenia: A severe emotional disorder of psychotic depth characteristically marked by a retreat from reality with delusion formation, HALLUCINATIONS, emotional disharmony, and regressive behavior.Schizophrenic Psychology: Study of mental processes and behavior of schizophrenics.Schizophrenia, Paranoid: A chronic form of schizophrenia characterized primarily by the presence of persecutory or grandiose delusions, often associated with hallucination.Sleep Paralysis: A common condition characterized by transient partial or total paralysis of skeletal muscles and areflexia that occurs upon awakening from sleep or less often while falling asleep. Stimuli such as touch or sound may terminate the episode, which usually has a duration of seconds to minutes. This condition may occur in normal subjects or be associated with NARCOLEPSY; CATAPLEXY; and hypnagogic HALLUCINATIONS. The pathophysiology of this condition is closely related to the normal hypotonia that occur during REM sleep. (From Adv Neurol 1995;67:245-271)Paranoid Disorders: Chronic mental disorders in which there has been an insidious development of a permanent and unshakeable delusional system (persecutory delusions or delusions of jealousy), accompanied by preservation of clear and orderly thinking. Emotional responses and behavior are consistent with the delusional state.Affective Disorders, Psychotic: Disorders in which the essential feature is a severe disturbance in mood (depression, anxiety, elation, and excitement) accompanied by psychotic symptoms such as delusions, hallucinations, gross impairment in reality testing, etc.Psychiatric Status Rating Scales: Standardized procedures utilizing rating scales or interview schedules carried out by health personnel for evaluating the degree of mental illness.Antipsychotic Agents: Agents that control agitated psychotic behavior, alleviate acute psychotic states, reduce psychotic symptoms, and exert a quieting effect. They are used in SCHIZOPHRENIA; senile dementia; transient psychosis following surgery; or MYOCARDIAL INFARCTION; etc. These drugs are often referred to as neuroleptics alluding to the tendency to produce neurological side effects, but not all antipsychotics are likely to produce such effects. Many of these drugs may also be effective against nausea, emesis, and pruritus.Auditory Perceptual Disorders: Acquired or developmental cognitive disorders of AUDITORY PERCEPTION characterized by a reduced ability to perceive information contained in auditory stimuli despite intact auditory pathways. Affected individuals have difficulty with speech perception, sound localization, and comprehending the meaning of inflections of speech.Prodromal Symptoms: Clinical or physiological indicators that precede the onset of disease.Lewy Body Disease: A neurodegenerative disease characterized by dementia, mild parkinsonism, and fluctuations in attention and alertness. The neuropsychiatric manifestations tend to precede the onset of bradykinesia, MUSCLE RIGIDITY, and other extrapyramidal signs. DELUSIONS and visual HALLUCINATIONS are relatively frequent in this condition. Histologic examination reveals LEWY BODIES in the CEREBRAL CORTEX and BRAIN STEM. SENILE PLAQUES and other pathologic features characteristic of ALZHEIMER DISEASE may also be present. (From Neurology 1997;48:376-380; Neurology 1996;47:1113-1124)Schizophrenia, Childhood: An obsolete concept, historically used for childhood mental disorders thought to be a form of schizophrenia. It was in earlier versions of DSM but is now included within the broad concept of PERVASIVE DEVELOPMENT DISORDERS.Early Medical Intervention: Action taken to reduce susceptibility or exposure to health problems and to detect and treat disease in early stages.Delirium, Dementia, Amnestic, Cognitive Disorders: Cognitive disorders including delirium, dementia, and other cognitive disorders. These may be the result of substance use, trauma, or other causes.Parkinson Disease: A progressive, degenerative neurologic disease characterized by a TREMOR that is maximal at rest, retropulsion (i.e. a tendency to fall backwards), rigidity, stooped posture, slowness of voluntary movements, and a masklike facial expression. Pathologic features include loss of melanin containing neurons in the substantia nigra and other pigmented nuclei of the brainstem. LEWY BODIES are present in the substantia nigra and locus coeruleus but may also be found in a related condition (LEWY BODY DISEASE, DIFFUSE) characterized by dementia in combination with varying degrees of parkinsonism. (Adams et al., Principles of Neurology, 6th ed, p1059, pp1067-75)Temporal Lobe: Lower lateral part of the cerebral hemisphere responsible for auditory, olfactory, and semantic processing. It is located inferior to the lateral fissure and anterior to the OCCIPITAL LOBE.Cognition Disorders: Disturbances in mental processes related to learning, thinking, reasoning, and judgment.Schizophrenic Language: The artificial language of schizophrenic patients - neologisms (words of the patient's own making with new meanings).Neuropsychological Tests: Tests designed to assess neurological function associated with certain behaviors. They are used in diagnosing brain dysfunction or damage and central nervous system disorders or injury.Designer Drugs: Drugs designed and synthesized, often for illegal street use, by modification of existing drug structures (e.g., amphetamines). Of special interest are MPTP (a reverse ester of meperidine), MDA (3,4-methylenedioxyamphetamine), and MDMA (3,4-methylenedioxymethamphetamine). Many drugs act on the aminergic system, the physiologically active biogenic amines.Alexia, Pure: Loss of the power to comprehend written materials despite preservation of the ability to write (i.e., alexia without agraphia). This condition is generally attributed to lesions that "disconnect" the visual cortex of the non-dominant hemisphere from language centers in the dominant hemisphere. This may occur when a dominant visual cortex injury is combined with underlying white matter lesions that involve crossing fibers from the occipital lobe of the opposite hemisphere. (From Adams et al., Principles of Neurology, 6th ed, p483)Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.