Organic brain syndrome

Organic brain syndrome is a general term which refers to physical disorders that cause a decrease in mental function, usually not including psychiatric disorders.

Alternative Names:
OBS; Organic mental disorder; Chronic organic brain syndrome

Causes, incidence, and risk factors:
OBS is a common “diagnosis” of the elderly. It is not an inevitable part of aging, however. OBS is not a separate disease entity, but is a general term used to categorize physical conditions that can cause mental changes.

Disorders associated with OBS include, but are not limited to:

  • Degenerative disorders:
    • Creutzfeldt-Jacob disease      
    • Huntington disease      
    • Multiple sclerosis      
    • Normal pressure hydrocephalus      
    • Pick’s disease      
    • Senile dementia/Alzheimer’s type


  • Cardiovascular disorders:

    • Arrhythmias - may cause some types of OBS      
    • Cardiac infections (endocarditis, myocarditis, etc.) - may sometimes cause OBS      
    • Hypertensive brain injury      
    • Multi-infarct dementia (multiple strokes)      
    • Stroke      
    • TIA


  • Trauma-induced brain injury:

    • Chronic subdural hematoma (blood clot causing pressure on brain)      
    • Concussion      
    • Intracerebral hemorrhage      
    • Subarachnoid hemorrhage


  • Dementia due to metabolic causes

  • Respiratory conditions - may cause or aggravate OBS

    • Hypoxia (decreased oxygen in the body)      
    • Hypercapnia (increased carbon dioxide levels in the body)


  • Infections

    • Any acute or chronic infection      
    • Septicemia (presence in the bloodstream of toxic by-products caused by infection)      
    • Meningitis      
    • Encephalitis


  • Drug and alcohol related conditions

    • Intoxication, drug abuse, or alcohol use      
    • Long-term effects of alcohol, Wernicke-Korsakoff syndrome      
    • Alcohol withdrawal state      
    • Withdrawal from drugs (especially sedative-hypnotics and corticosteroids)


  • Parkinson’s disease

Other conditions that may be related to organic brain syndrome include: depression, neuroses, and psychoses of various types, which may occur simultaneously with the OBS.

Symptoms vary with the specific disease. In general, organic brain syndromes cause varying extents of confusion, delirium (severe, short-term losses of brain function), agitation, and dementia (long-term, often progressive, losses of brain function).

Signs and tests:
Testing and physical examination vary depending on the specific disorder.

Treatment varies with the specific disorder. Many of the disorders have nonspecific treatments - primarily supportive care to assist the person in areas where brain function is lost.

Medications may be needed to reduce aggressive behaviors typical of some of the conditions in this category.

Expectations (prognosis):
See the specific disorder. Some disorders are acute and treatable, but many are chronic or progressive.

Loss of ability to interact or function independently is common.

Calling your health care provider:
Call your health care provider if “organic brain syndrome” has been diagnosed and you are uncertain of the actual, specific diagnosis; if you have symptoms which suggest this problem; or if you have been diagnosed with it and symptoms become worse.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.