Organic brain syndrome, also known as organic brain disease, organic brain disorder, organic mental syndrome, or organic mental disorder, refers to any syndrome or disorder of mental function whose cause is alleged to be known as organic (physiologic) rather than purely of the mind. These names are older and nearly obsolete general terms from psychiatry, referring to many physical disorders that cause impaired mental function. They are meant to exclude psychiatric disorders (mental disorders). Originally, the term was created to distinguish physical (termed "organic") causes of mental impairment from psychiatric (termed "functional") disorders, but during the era when this distinction was drawn, not enough was known about brain science (including neuroscience, cognitive science, neuropsychology, and mind-brain correlation) for this cause-based classification to be more than educated guesswork labeled with misplaced certainty, which is why it has been deemphasized in current medicine. While mental or behavioural abnormalities related to the dysfunction can be permanent, treating the disease early may prevent permanent damage in addition to fully restoring mental functions. An organic cause to brain dysfunction is suspected when there is no indication of a clearly defined psychiatric or "inorganic" cause, such as a mood disorder. Types
Organic brain syndrome can be divided into 2 major subgroups: acute (delirium or acute confusional state) and chronic (dementia). A third entity, encephalopathy (amnestic), denotes a gray zone between delirium and dementia.
Damage to brain functioning could be due not only to organic (physical) injury (a severe blow to the head, stroke, chemical and toxic exposures, organic brain disease, substance use, etc.) and also to non-organic means such as severe deprivation, abuse, neglect, and severe psychological trauma. Symptoms
Many of the symptoms of Organic Mental Disorder depend on the cause of the disorder, but are similar and include physical or behavioral elements. Dementia and delirium are the cause of the confusion, orientation, cognition or alertness impairment. Therefore, these symptoms require more attention because hallucinations, delusions, amnesia, and personality changes are the result. These effects of the dementia and delirium are not joined with the changes of sensory or perception abilities. Memory impairment, judgment, logical function and agitation are also some extremely common symptoms. The more common symptoms of OBS are confusion; impairment of memory, judgment, and intellectual function;  and agitation. Often these symptoms are attributed to psychiatric illness, which causes a difficulty in diagnosis. Associated conditions
Disorders that are related to injury or damage to the brain and contribute to OBS include, but are not limited to:

Alcoholism
Alzheimers disease
Attention deficit/hyperactivity disorder
Autism
Concussion
Encephalitis
Epilepsy
Fetal alcohol syndrome
Hypoxia
Parkinsons disease
Intoxication/overdose caused by substance use disorders including alcohol use disorder
Non-medical use of sedative hypnotics
Intracranial hemorrhage/trauma
Korsakoff syndrome
Mastocytosis
Meningitis
Psychoorganic syndrome
Stroke/transient ischemic attack (TIA)
Withdrawal from drugs, especially sedative hypnotics, e.g. alcohol or benzodiazepinesOther conditions that may be related to organic brain syndrome include: clinical depression, neuroses, and psychoses, which may occur simultaneously with the OBS.