Cognitive Disorders – Causes, Signs and Symptoms

Cognitive Disorders

Also called: Social Cognitive Disorders


Cognitive disorders are mental conditions that cause patients to have difficulty thinking. Although symptoms of these disorders vary, they are generally marked by impaired awareness, perception, reasoning, memory and judgment.

Cognition involves the mental processing of information. Memory and thought combine to store, retrieve and manipulate this information. When something goes wrong with this process, a cognitive disorder may result.

There are four major categories of cognitive disorders:

  • Delirium. A change in consciousness that develops over a short period of time, typically a few hours to days. Patients find it difficult to pay attention or to think clearly and have reduced awareness of their environment.

  • Dementia. A progressive deterioration of brain function that is marked by impairment of memory, confusion and inability to concentrate.

  • Amnestic disorder (amnesia). Involves a significant loss of the memory, although there is no loss of other cognitive functions as there is in dementia.

  • Cognitive disorder, not otherwise specified (NOS). Includes cognitive impairment and is presumed to be due to a general medical condition or substance use and does not fit into the other categories.

A wide variety of factors can lead to cognitive disorders, including general medical conditions, brain infections and head injury. Symptoms experienced by patients vary depending on the nature of the disorder that is present, but may include rapid shifting of consciousness, confusion and impaired memory.

Cognitive disorders are typically diagnosed following physical and neurological examinations. Imaging tests, blood tests and other tests (e.g., liver function tests, thyroid tests) may also be performed.

Treatment options differ depending on which condition is present. Though delirium can usually be treated effectively by addressing the underlying condition, the prognosis may be less optimistic for patients with dementia or amnesia.

About cognitive disorders

Cognitive disorders are mental conditions characterized by impaired awareness, perception, reasoning, memory and judgment. Patients with these disorders have difficulty with the basic process of thinking.

Cognition is the act of mentally processing information. Memory and thought combine to store, retrieve and manipulate this information. When something goes wrong with an individual’s memory or thought processes, a cognitive disorder may result. Problems with memory, orientation, language, information processing, and the ability to focus or finish a task are all characteristic of cognitive disorders.

The American Psychiatric Association (APA) recognizes four major categories of cognitive disorders. They included:

  • Delirium. The most common cognitive disorder, delirium involves a change in consciousness that develops over a short period of time, typically a few hours to days. Patients find it difficult to pay attention or to think clearly and have reduced awareness of their environment and/or self. Episodes of delirium usually begin suddenly and may come and go over the course of a day. Patients are often more lucid in the morning than they are in the evening. Most episodes of delirium resolve within one week, although the disorder can evolve into dementia or amnestic disorder (amnesia). Delirium should always be considered a medical emergency.
  • Dementia. A chronic and progressive deterioration of brain function marked by impairment of memory (all cases involve amnesia), confusion and the ability to concentrate. In most cases, dementia is difficult to treat and becomes progressively worse over time. Patients initially may forget only recent memories, but as the disease progresses older memories may also be impaired. Patients may also fail to recognize familiar objects (agnosia), have trouble freely conversing (aphasia), fail to perform certain motor acts (apraxia) or have trouble performing complex behaviors (loss of executive functioning). Dementia typically develops gradually and is most often found in elderly people.
  • Amnesia. Involves a significant loss of memory, although there is no associated loss of other cognitive functions as there is with dementia. Amnesia can be devastating to those with the condition. Patients may even forget events that took place only a few minutes earlier. Another type of amnesia called dissociative amnesia is a separate condition that occurs when a person loses memories related to a traumatic event (e.g., war or abuse).
  • Cognitive disorders, not otherwise specified (NOS). Includes cognitive impairment that is thought to result from a general medical condition or substance use and does not fit into the other categories.

Potential causes of cognitive disorders

A wide variety of factors can lead to cognitive disorders. Delirium is usually the result of an underlying brain condition, especially a lack of oxygen to the brain (hypoxia). Conditions such as acute meningitis or encephalitis (infections of the brain) are also associated with delirium, as are general medical conditions, use of certain medications, intoxication with or withdrawal from drugs and/or alcohol, or exposure to toxins. Delirium usually reverses itself with successful treatment of the underlying medical disorder that triggered the condition.

Dementia is often the result of a condition that impairs the blood vessels or nerve structures in the brain. In some cases, these conditions are treatable, as is often the case with normal pressure hydrocephalus (brain disorder caused by blockage in the flow of cerebrospinal fluid), brain tumors and certain metabolic causes and infections. Research also indicates that people who consume regular quantities of omega-3 fatty acids (naturally found in fish and flaxseed) are much less likely to develop dementia than those who do not. More often, disorders that cause dementia are largely untreatable and irreversible.

The two major sources of dementia are Alzheimer’s disease (a progressive, degenerative brain disease that accounts for more than half of all cases of dementia, according to the American Psychiatric Association [APA]) and vascular dementia (loss of brain function due to a series of small strokes). The two conditions often strike at the same time.

Many other conditions also can cause dementia, including:

  • Head trauma.

  • Infection with human immunodeficiency virus (HIV).

  • Huntington’s disease. A progressive disorder involving wasting (degeneration) of nerve cells in the brain.

  • Creutzfeldt-Jakob disease. Also known as “mad cow disease,” a neurodegenerative disease caused by a protein-like particle called a prion.

  • Parkinson’s disease. Disease associated with damage to a part of the brain involved with movement.

  • Pick’s disease. Disease similar to Alzheimer’s that tends to affect only certain areas of the brain.

  • Substance abuse.

Amnestic disorder (amnesia) can be caused by a general medical condition (such as a physical injury, chronic alcoholism or vitamin deficiency) or by use of certain substances, including medications such as sedatives, hypnotics and anxiolytics. Patients who have amnesia may have difficulty recalling past events or learned information. In addition, they may struggle to learn new information. The damage to memory caused by amnesia may be reversible, depending on the cause.

Amnesia is most often seen in older patients who experience damage from years of alcoholism or malnutrition (especially from lack of the B vitamin thiamine), or from trauma to the brain. However, amnesia can also affect younger patients who suffer head trauma from falls, automobile accidents, wounds, infection, tumors, strokes or surgery.  

Other conditions associated with amnesia include:

  • Brain inflammation caused by herpes (herpes simplex encephalitis)
  • Injury to the brain without skull fracture (closed-head trauma)
  • Hypoxia (deficiency of oxygen in the tissues)
  • Penetrating head wounds (e.g., gunshot wounds)
  • Stroke
  • Surgery

Signs and symptoms of cognitive disorders

Symptoms experienced by patients vary depending on the nature of the cognitive disorder that is present. For example, rapid shifting of consciousness is the major characteristic of delirium. Patients have episodes of disorientation and may shift from feelings of lethargy to sudden agitation before quickly becoming lethargic again.

Dementia is characterized by progressive declining of cognitive functions such as worsening  confusion and impaired ability to recognize people or places that should be familiar to the patient. Patients with Alzheimer’s disease may initially appear to exhibit a change in personality in which existing personality traits – such as a tendency to be secretive or to obsess about things – become magnified. Memory loss is also commonly associated with early stages of Alzheimer’s. Over time, patients will become increasingly disoriented until they reach a point of being unable to provide the most basic forms of self-care. In contrast to Alzheimer’s disease, vascular dementia tends to cause more rapid deterioration induced by a series of small strokes.

Amnestic disorders are marked by difficulty recalling past events or learned information, as well as problems learning new information. Patients generally have more trouble remembering recent information than they do recalling more distant memories. Patients may also feel disorientation in regard to time and place.

Other symptoms that may be present in those who have cognitive disorders include:

  • Inability to concentrate
  • Memory problems
  • Hallucinations and delusions
  • Altered sensation or perception
  • Altered sleep patterns
  • Motor system impairment
  • Speech difficulties
  • Disorientation
  • Personality or emotional changes
  • Difficulty paying attention or following instructions

The symptoms of cognitive disorders must be carefully analyzed before a diagnosis is made. Many other mental illnesses – such as depression, anxiety and psychosis – share symptoms with cognitive disorders.

Diagnosis methods for cognitive disorders

Patients are likely to seek medical care when they or their loved ones become concerned about deterioration of cognitive functioning. The physician will perform a complete physical examination and compile a thorough medical history.

A neurological examination may be performed to check for abnormalities in reflexes and other potential indicators of cognitive disorders. Testing may include studies of the patient’s psychological makeup, cognitive function, motor function and levels of sensation.

Imaging tests such as CAT (computed axial tomography) scans and MRI (magnetic resonance imaging)  may help a physician to detect brain abnormalities responsible for delirium and dementia, and some types of amnestic disorder (amnesia). Blood testing may also be performed to measure levels of blood cells, electrolytes, calcium, magnesium, glucose, thyroid hormones, liver enzymes and creatine phosphokinase.

Other tests that may be performed include:

  • Electroencephalogram (EEG)

  • Positron emission tomography (PET) scan

  • Cerebrospinal fluid (CSF) analysis of fluid near the brain and spinal cord

  • Chest x-ray

  • Urinalysis testing

  • Drug and alcohol testing (of blood and urine)

New tools are also being developed, such as the “Dementia Risk Score,” to help predict a person’s risk of developing dementia, which many experts believe can be delayed or prevented with lifestyle modifications (e.g., exercising regularly, consuming a balanced diet) and drug therapies. Patients who are diagnosed with cognitive disorders have experienced a significant change from their previous level of functioning. The specific criteria for diagnosing individual cognitive disorders vary by disorder.

Treatment options for cognitive disorders

Treatment of delirium focuses on relieving the underlying condition that is causing the delirium. The method of therapy will differ depending on the disease or disorder to be treated.

Treatment of dementia is focused on controlling the symptoms that are associated with this disorder. Symptoms vary significantly from patient to patient, and treatments – generally medications – will be given to the patient based on what is appropriate. Patients often have to be monitored closely in a home or hospital. This is especially true as the disorder progresses and symptoms become more severe.

Treatments for amnestic disorder (amnesia) treatments vary in their success levels. Some cases improve when the underlying conditions have been treated. For example, patients who experience a deficiency in the B vitamin thiamine may reverse their symptoms by improving their nutrition. In others, the memory problems may be irreversible.

In some cases, symptoms related to cognitive disorders can be reduced by stopping or lowering the dosage level of certain medications known to increase confusion. These include:

  • Alcohol and illegal drugs
  • Analgesics (medications that relieve pain)
  • Anticholinergics (medications that relax the muscles)
  • Central nervous system (CNS) depressants
  • Cimetidine (used to treat gastrointestinal disorders)
  • Lidocaine (an anesthetic)
  • Anti-anxiety drugs (medications to treat anxiety)

Certain medical conditions may also cause added confusion in patients who have cognitive disorders. Treating the following conditions can ease such feelings of confusion:

  • Heart failure
  • Decreased oxygen (hypoxia)
  • Excessive carbon dioxide levels (hypercapnia)
  • Thyroid disorders
  • Anemia (abnormally low levels of red blood cells)
  • Nutritional disorders
  • Infections
  • Kidney failure
  • Liver failure
  • Psychiatric conditions such as depression

Some patients with cognitive disorders may engage in aggressive or violent behavior that can be treated with various supplements and medications, such as the B vitamin thiamine, sedatives, dopamine blockers, selective serotonin reuptake inhibitors(SSRIs) and antidepressants. Antipsychotic drugs can also be used to relieve agitation associated with these disorders. In some cases, these patients will require hospitalization and monitoring or restraints to prevent them from hurting themselves or others.

In addition, researchers recently discovered a gene called Kibra that is thought to play a significant role in memory performance in humans. This discovery may lead to the development of new treatments for various cognitive disorders. Additionally, a vaccine for Alzheimer’s disease is currently being developed

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to cognitive disorders:

  1. How will you determine whether or not I have a cognitive disorder?
  2. Why do you suspect I have a cognitive disorder?
  3. What is the likely cause of my cognitive disorder?
  4. What symptoms can I expect as my disorder progresses?
  5. What is the prognosis for my cognitive disorder?
  6. What are my treatment options?
  7. Are there certain medications I should avoid that may trigger symptoms?
  8. Are the symptoms associated with my cognitive disorder reversible?
  9. What are my long-term prospects for being able to live independently?
  10. Should I begin looking into long-term care options?
  11. I have a relative who was diagnosed with a cognitive disorder. What is my risk of developing the same condition?
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