Organic brain syndrome (OBS) is a general term that refers to diseases (usually not psychiatric disorders) that cause decreased mental function.

OBS is common in the elderly. It is not a part of the normal aging process, however.

OBS is not a separate disease, but is a general term used to describe physical conditions that can cause mental changes.

Disorders associated with OBS include:

• Brain injury caused by trauma
  • Bleeding into the brain (intracerebral hemorrhage)
  • Bleeding into the space around the brain (subarachnoid hemorrhage)
  • Blood clot causing pressure on brain (chronic subdural hematoma)
  • Concussion
• Breathing conditions
  • Low oxygen in the body (hypoxia)
  • High carbon dioxide levels in the body (hypercapnia)
• Cardiovascular disorders
  • Abnormal heart rhythm (arrhythmias)
  • Brain injury due to high blood pressure (hypertensive brain injury)
  • Dementia due to many strokes (multi-infarct dementia)
  • Heart infections (endocarditis, myocarditis)
  • Stroke
  • Transient ischemic attack (TIA)
• Degenerative disorders
  • Creutzfeldt-Jacob disease
  • Diffuse Lewy Body disease
  • Huntington's disease
  • Multiple sclerosis
  • Normal pressure hydrocephalus
  • Parkinson's disease
  • Pick's disease
  • Senile dementia, Alzheimer's type
• Dementia due to metabolic causes
• Drug and alcohol-related conditions
  • Alcohol withdrawal state
  • Intoxication, drug abuse, or alcohol use
  • Long-term effects of alcohol, Wernicke-Korsakoff syndrome
  • Withdrawal from drugs (especially sedative-hypnotics and corticosteroids)
• Infections
  • Any sudden onset (acute) or long-term (chronic) infection
  • Blood poisoning (septicemia)
  • Swelling of the brain (encephalitis)
  • Swelling of the lining of the brain and spinal cord (meningitis)
• Other medical disorders
  • Cancer
  • Kidney disease
  • Liver disease
  • Thyroid disease (high or low)
  • Vitamin deficiency (B12 and others)

Other conditions that may be related to organic brain syndrome include:

• Depression
• Neurosis
• Psychosis