Behavior, unusual or strange

Alternative names:

acting strangely

Definition:

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

Considerations:

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

Note: There may be other causes of unusual or strange behavior. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as quality, time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for unusual or strange behavior, occurring alone or in combination with other problems.