What is "organic brain syndrome"

n. mental abnormality resulting from disturbance of the structure or function of the brain

An organic brain syndrome (OBS), also known as an organic brain disease/disorder (OBD), an organic mental syndrome (OMS), or an organic mental disorder (OMD), is a 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 etiologic classification to be more than educated guesswork labeled with misplaced certainty, which is why it has been deemphasized in current medicine.

Acute organic brain syndrome is (by definition) a recently appearing state of mental impairment, as a result of intoxication, drug overdose, infection, pain, and many other physical problems affecting mental status. In medical contexts, "acute" means "of recent onset". As is the case with most acute disease problems, acute organic brain syndrome is often temporary–however this is not guaranteed (a recent-onset problem may continue to be chronic or long term). A more specific medical term for the acute subset of organic brain syndromes is delirium.

Chronic organic brain syndrome is long-term. For example, some forms of chronic drug or alcohol dependence can cause organic brain syndrome due to their long-lasting or permanent toxic effects on brain function. Other common causes of chronic organic brain syndrome sometimes listed are the various types of dementia, which result from permanent brain damage due to strokes, Alzheimer's disease, or other damaging causes which are not reversible.

Though OBS was once a common diagnosis in the elderly, until the understanding of the various types of dementias it is related to a disease process and is not an inevitable part of aging. In some of the older literature, there was an attempt to separate organic brain syndrome from dementia, but this was related to an older world view in which dementia was thought to be a part of normal aging, and thus did not represent a special disease process. The later identification of various dementias as clear pathologies is an example of the types of pathological problems discovered to be associated with mental states, and is one of the areas which led to abandonment of all further attempts to clearly define and use OBS as a term.