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What causes personality change? 17 possible conditions

What Characterizes Strange or Unusual Behavior?

Unusual or strange behavior is behavior that is not appropriate to the circumstances. It occurs when a person is unnaturally moody, aggressive, euphoric, or mild-tempered. Fluctuations in mood from time to time are normal. However, unusual reactions to events may be a sign of a medical or mental disorder. Some examples are being happy to hear tragic news or being nonchalant in situations that would normally cause stress or aggravation.

When Is Unusual Behavior a Cause for Concern?

Grief, bad news, and disappointment can cause a normally happy person to become downtrodden. Sometimes, a person’s mood can be altered for weeks or months after hearing devastating news.

However, some people experience unusual or strange behavior for years. This usually occurs if they have been through a traumatic change or witnessed an unpleasant event.

These behavioral changes may be caused by a mental disorder, such as:

  • Anxiety: Anxiety occurs when a person feels nervous or uneasy about a situation. It is normal to experience some anxiety, but when it occurs on a regular basis without provocation, it may be a sign of generalized anxiety disorder.
  • Panic attacks: Panic attacks are periods of extreme fear. Sometimes, the fear seems to be irrational. Such situations include a person having a panic attack when seeing an elevator or speaking in public.
  • Posttraumatic stress disorder: Posttraumatic stress disorder, also called PTSD, is a mental condition marked by extreme fear, flashbacks, and hallucinations. This condition is triggered by memories of trauma, such as a terrorist attack or car accident.
  • Bipolar disorder: Bipolar disorder causes a person to have extreme fluctuations in mood. Bipolar disorder is marked by a quick switch between being happy and being upset. The switch is often extreme, causing a person to act out when hearing disagreeable things.
  • Schizophrenia: Schizophrenia is a mental disorder that makes it difficult to think clearly, to have normal emotions, to behave normally in social situations, and to distinguish between what is real and what is not real.

Medical conditions that cause a fluctuation in hormone levels can also cause strange or unusual behavior. These conditions include:

  • menopause
  • premenstrual syndrome (PMS)
  • andropause (male menopause)
  • hyperthyroidism/hypothyroidism (an over- or under-active thyroid gland)

Medical emergencies can also cause strange or unusual behavior. These situations include:

  • heart attack
  • stroke
  • dehydration
  • malnutrition

When Is Unusual Behavior a Medical Emergency?

Look for the following signs to determine if strange or unusual behavior is an emergency situation:

  • weak pulse
  • clammy skin
  • rapid heart rate
  • rapid breathing
  • shallow breathing
  • low blood pressure
  • confusion
  • dizziness
  • lightheadedness
  • difficulty talking
  • shooting pains in the arms or legs
  • pain in the chest
  • visual changes

If you or a loved one experiences any of these symptoms, seek medical attention immediately. Do not drive yourself to a hospital. Call 911.

Diagnosing Unusual Behavior

If you’ve been experiencing unusual or strange behavior, speak to your doctor about it. Make sure to note

  • when the strange behavior began
  • what times of day you experience it
  • what triggers it
  • whether it happens after taking prescription medication (bring the prescription with you)
  • if you are taking drugs
  • if you’re using alcohol
  • if you have a history of mental disorders
  • if your family has a history of mental disorders
  • any other symptoms you may be experiencing
  • if you have any underlying medical conditions

The answers to these questions will be extremely helpful to your doctor. They will help him or her diagnose the cause of your unusual behavior. They will also assist him or her in determining whether your problem is a mental or medical issue.

The doctor may choose to run tests. These may include a complete blood count, glucose level test, hormone profile, and tests for infections. If you have no discernible medical condition, he or she will refer you to a mental health specialist.

Treating Unusual or Strange Behavior

Unusual or strange behavior caused by a medical condition, such as hypothyroidism, may subside once the condition is treated. However, in some cases, this symptom will not go away with treatment of the underlying condition. In this case, you must be treated separately using mood-altering medications.

If you have a hormonal imbalance, the strange behavior may subside after being prescribed medications to balance your hormones. Replacement estrogen, low-dose birth control pills, and progesterone injections are commonly prescribed medicines.

Mental health conditions may be treated with a combination of mood-altering medications and therapy. Doctors typically prescribe medications to treat conditions such as anxiety disorder, panic disorder, PTSD, and bipolar disorder. Psychotherapy, also called talk therapy, might also be recommended to help you learn to cope with stressful situations.

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See a list of possible causes in order from the most common to the least.



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Head Injury

This condition is considered a medical emergency. Urgent care may be required.

A head injury could be an injury to the brain, skull, or scalp. It can vary in severity depending on the cause. In some cases face swelling can be a sign of a head injury.

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Dementia Overview

Dementia may affect memory, thinking, language, judgment, and behavior. Mental impairment must affect at least two brain functions to be considered dementia.

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What is Alzheimer's Disease?

Alzheimer's disease (AD), the most common cause of dementia, is a progressive brain disorder. Learn about the causes, signs and research being done about AD.

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Stroke Overview

This condition is considered a medical emergency. Urgent care may be required.

A stroke (a "brain attack") is a medical emergency in which part of the brain is deprived of oxygen. This occurs when an artery that supplies oxygenated blood to the brain becomes damaged and brain cells begin to die.

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Adult Brain Tumor

A brain tumor is the growth of abnormal cells in your brain. Whether the growth is cancerous or not, any brain tumor is serious. Symptoms can include both cognitive and physical control problems.

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Creutzfeldt-Jakob Disease and Mad Cow Disease

Creutzfeldt-Jakob disease is an infectious disease that causes the brain to degenerate. The hallmark of this brain disease is an inability to think clearly and take care of oneself.

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Primary Cerebral Lymphoma

Primary cerebral lymphoma is also known as brain lymphoma or central nervous system lymphoma. The brain and spinal cord make up the central nervous system. Cells called lymphocytes are part of the lymph system and ca...

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Pituitary Cancer

The pituitary gland is a very small gland of major importance to the functioning of the human body. It is located directly behind the eyes and below the front of the brain. It is about the size of a pea. Despite it...

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Epilepsy Overview

Epilepsy is a neurological condition caused by malfunctioning brain cells that result in seizures. There is no cure for this disorder but episodes can become less frequent.

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Central Sleep Apnea

Central sleep apnea is a sleep disorder in which you briefly stop breathing during sleep. The moments of apnea can occur repeatedly throughout the night. The interruption of your breathing happens may indicate a proble...

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Huntington's Disease

Huntington's disease is a hereditary condition in which the brain's nerve cells gradually break down. This affects physical movements, emotions, and cognitive abilities. There is no cure, but there are ways to cope wit...

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Porphyrias are rare types of genetic blood disorders in which patients have a defect in heme production, an important part of hemoglobin. Blisters are a sign of porphyria cutanea tarda, the most common type of porphyria.

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Post Concussion Syndrome

Post-concussion syndrome, or post-concussive syndrome (PCS), refers to the lingering symptoms following a concussion or a mild traumatic brain injury. Symptoms vary but include headache, dizziness, and depression.

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Pernicious Anemia

Pernicious anemia (PA) is an autoimmune disorder in which the body fails to make enough healthy red blood cells (RBCs), resulting in vitamin B-12 deficiency. Most people experience a burning or sore tongue.

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In hyperparathyroidism, the parathyroid glands make too much of their hormone. It affects a number of body systems and can cause skin changes, including brittle nails and itching.

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Brain Tumor

A brain tumor is a collection or mass of abnormal cells in your brain. A brain tumor can be cancerous (malignant) or non-cancerous (benign).

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This feature is for informational purposes only and should not be used to diagnose.
Please consult a healthcare professional if you have health concerns.