Behavior - Unusual


Abnormally strange, unusual, or weird behavior in a person that is not typical of that individual (delirium or dementia).

Alternative Names
Acting strangely

Delirium differs from dementia in that it indicates fluctuating or reversible behavior whereas most dementias are progressively deteriorating behavior.

Delirium usually consists of disorientation and confusion, whereas dementia, in the earlier stages, usually consists of memory deficits. Senile dementia (confusion) is a major problem in America today because people are living longer than ever before.

Elderly people are often diagnosed as “senile” yet this diagnosis is made incorrectly or prematurely. There are many causes of strange behavior that need to be explored before a diagnoses like Alzheimer’s disease (senile dementia) is made. Alzheimer’s disease is a specific type of dementia.

Common Causes
(in older people)

  • malnutrition (particularly vitamin B12 and thiamine deficiency)  
  • medications  
  • alcohol in excess  
  • chronic exposure to cold (hypothermia)  
  • emotional problems (depression or feeling useless)  
  • Head injury (subdural hematoma)  
  • unfamiliar surroundings  
  • dehydration  
  • electrolyte abnormality  
  • infection (including pneumonia, gastroenteritis, urinary tract infection)  
  • thyroid disorders (either underactive or overactive)  
  • Alzheimer’s disease

(in people of all ages):

  • anxiety, emotional problems  
  • amphetamines and antidepressants  
  • illicit drug use  
  • diseases affecting the nervous system (neurological diseases)  
  • non-neurological diseases, particularly with fever (for example, pneumonia)  
  • low or high thyroid function  
  • environmental hazards

Home Care
For dementia or delirium caused by a brain tumor, Head injury, stroke, infection, fever, or pneumonia, see the doctor about the proper treatment for the underlying cause.

For delirium caused by anxiety and emotional problems, reassurance and loving support are recommended. Frequent feedback about time, place, and names of people providing care can be helpful.

For delirium or dementia caused by malnutrition, a proper diet and vitamin supplements are recommended.

For delirium caused by medication, consult your doctor about adjusting dosage, changing medications, or discontinuing them.

For delirium or dementia caused by alcohol in excess, complete abstinence is required.

For delirium caused by emotional problems, psychological counseling is recommended.

For delirium caused by hypothermia, adequate heat and warmth is required. Re-warming should be carefully monitored.

For delirium that follows surgery, this condition is usually temporary, but avoid prolonged use of sedatives and pain killers.

For dementia caused by Alzheimer’s disease, there is no prevention but possible new treatments should be discussed with the doctor (for example, Cognex). Sympathetic care, occupational therapy, and family support are needed.

For dementia caused by Huntington’s chorea, provide supportive care.

For delirium resulting from environmental causes, make a concerted effort to modify the environment or change environments.

For delirium caused by low thyroid function, see the doctor about thyroid hormone replacements.

Call your health care provider if

  • dementia or delirium is present.  
  • unusual or strange behavior is severe, prolonged, unexplained, or is impairing lifestyle.

Note: Often a neurologist is the doctor of choice.

What to expect at your health care provider’s office

The medical history will be obtained and a physical examination performed.

Medical history questions documenting unusual or strange behavior in detail may include:

  • quality
    • What unusual behaviors are present?      
    • How much is the lifestyle affected?      
    • Can the person eat, dress, and perform other everyday activities?


  • time pattern

    • When did the unusual behavior begin?      
    • Is it getting worse, better, or staying about the same?      
    • How fast is the behavior changing?


  • other

    • What other symptoms are also present?

The physical examination will probably include a detailed neurological evaluation.

Diagnostic tests that may be performed include:

  • a CT scan of the head  
  • other neurological tests  
  • blood tests

After seeing your health care provider:

If a diagnosis was made by the health care provider as the cause of unusual behavior, you may want to note that diagnosis in your personal medical record.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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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.