Definition of Behavior - unusual or strange:

Unusual or strange behavior involves performing actions that are not normal for the person.

Considerations:

Unusual or strange behavior may include:

• Loss of memory that continues over time or gets worse
• Loss of the ability to concentrate and perform other mental tasks

Common Causes:

There are many causes of unusual or strange behavior, including medical and psychiatric illnesses. Two of the more common medical causes are:

• Delirium -- Sudden or quick onset of reduced consciousness, awareness, perception, or thought that may be a symptom of a medical illness such as brain or mental dysfunction
• Dementia -- Chronic, worsening loss of cognitive function that occurs with brain disorders

Psychiatric illnesses that are often associated with unusual or strange behavior include:

• Anxiety disorder
• Bipolar disorder
• Depression
• Psychosis
• Schizophrenia

Possible causes of strange behavior in older people include:

• Alcohol consumption in excess
• Alzheimer's disease
• Chronic exposure to cold (hypothermia)
• Dehydration
• Hypoglycemia
• Electrolyte abnormality
• Emotional problems (depression or feeling useless)
• Head injury (subdural hematoma)
• Heart attack, pulmonary embolism, stroke
• Infection (including pneumonia, gastroenteritis, urinary tract infection)
• Malnutrition (particularly vitamin B12 and thiamine deficiency)
• Medications (sleeping pills, pain relievers)
• Thyroid disorders (either underactive or overactive)
• Unfamiliar surroundings

Possible causes in people of all ages include:

• Diseases affecting the nervous system (neurological diseases)
• Recreational drugs (such as amphetamines and cocaine)
• Environmental hazards
• Low or high thyroid function
• Non-neurological diseases, especially those with fever (for example, pneumonia)
• Side effects of medications