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Cognitive disorders (CDs), also known as neurocognitive disorders (NCDs), are a category of mental health disorders that primarily affect
cognitive abilities Cognitive skills, also called cognitive functions, cognitive abilities or cognitive capacities, are brain-based skills which are needed in acquisition of knowledge, manipulation of information and reasoning. They have more to do with the mechanisms ...
including learning, memory, perception, and problem solving. Neurocognitive disorders include
delirium Delirium (also known as acute confusional state) is an organically caused decline from a previous baseline of mental function that develops over a short period of time, typically hours to days. Delirium is a syndrome encompassing disturbances ...
, mild neurocognitive disorders, and major neurocognitive disorder (previously known as
dementia Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
). They are defined by deficits in cognitive ability that are acquired (as opposed to developmental), typically represent decline, and may have an underlying brain pathology. The
DSM-5 The ''Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition'' (DSM-5), is the 2013 update to the ''Diagnostic and Statistical Manual of Mental Disorders'', the taxonomic and diagnostic tool published by the American Psychiatric ...
defines six key domains of cognitive function: executive function, learning and memory, perceptual-motor function,
language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of ...
, complex attention, and social cognition. Although Alzheimer's disease accounts for the majority of cases of neurocognitive disorders, there are various medical conditions that affect mental functions such as memory, thinking, and the ability to reason, including frontotemporal degeneration,
Huntington's disease Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an uns ...
,
dementia with Lewy bodies Dementia with Lewy bodies (DLB) is a type of dementia characterized by changes in sleep, behavior, cognition, movement, and regulation of automatic bodily functions. Memory loss is not always an early symptom. The disease worsens over time an ...
,
traumatic brain injury A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity (ranging from mild traumatic brain injury TBI/concussionto severe traumatic b ...
(TBI),
Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
, prion disease, and dementia/neurocognitive issues due to HIV infection. Neurocognitive disorders are diagnosed as mild and major based on the severity of their symptoms. While
anxiety disorder Anxiety disorders are a cluster of mental disorders characterized by significant and uncontrollable feelings of anxiety and fear such that a person's social, occupational, and personal function are significantly impaired. Anxiety may cause physi ...
s, mood disorders, and psychotic disorders can also have an effect on cognitive and memory functions, they are not classified under neurocognitive disorders because loss of cognitive function is not the primary (causal) symptom. Additionally, developmental disorders such as
autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...
typically have a genetic basis and become apparent at birth or early in life as opposed to the acquired nature of neurocognitive disorders. Causes vary between the different types of disorders but most include damage to the memory portions of the brain. Treatments depend on how the disorder is caused. Medication and therapies are the most common treatments; however, for some types of disorders such as certain types of
amnesia Amnesia is a deficit in memory caused by brain damage or disease,Gazzaniga, M., Ivry, R., & Mangun, G. (2009) Cognitive Neuroscience: The biology of the mind. New York: W.W. Norton & Company. but it can also be caused temporarily by the use ...
, treatments can suppress the symptoms but there is currently no cure.


Classifications

The previous edition of the '' Diagnostic and Statistical Manual of Mental Disorders'' (DSM-IV) included a section entitled "Delirium, Dementia and Amnestic and Other Cognitive Disorders," which was revised in
DSM-5 The ''Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition'' (DSM-5), is the 2013 update to the ''Diagnostic and Statistical Manual of Mental Disorders'', the taxonomic and diagnostic tool published by the American Psychiatric ...
to the broader "Neurocognitive Disorders." Neurocognitive disorders are described as those with "a significant impairment of cognition or memory that represents a marked deterioration from a previous level of function". The main principle distinguishing neurocognitive disorders from mood disorders and other psychiatric conditions that involve a cognitive component (i.e. increased lapses in memory noted by patients with depression) is that cognitive decline is the "defining characteristic" of the disorder. Additionally, the term "neurocognitive" was added because these disorders most often have alterations/disfunction in neural physiology (i.e. amyloid plaque build-up in Alzheimer disease). The subsections include delirium, mild neurocognitive disorder, and major neurocognitive disorder.


Delirium

Delirium Delirium (also known as acute confusional state) is an organically caused decline from a previous baseline of mental function that develops over a short period of time, typically hours to days. Delirium is a syndrome encompassing disturbances ...
is a type of neurocognitive disorder that develops rapidly over a short period of time. Delirium may be described using many other terms, including: encephalopathy, altered mental status, altered level of consciousness, acute mental status change, and brain failure. It is described in the DSM-5 as a fluctuating acute change in mental status with associated changes in cognition, attention, and level of consciousness. The onset of delirium can vary from minutes to hours and sometimes days. However, the course of the delirium typically lasts from a few hours to weeks, depending on the underlying cause. Delirium can also be accompanied by a shift in attention, mood swings, violent or unordinary behaviors, and hallucinations. Additionally, changes in cognition can makes situational awareness and processing new information very difficult for patients. Delirium is most common in hospitalized patients, appearing in 18-35% of patients requiring hospital admission. It is also a diagnosis which can be acquired during hospital stays, typically by elderly patients or those with risk factors of delirium. While it is a common diagnosis, delirium can increase the risk of a longer hospital stay and the risk of complications throughout the hospital stay.


Mild Neurocognitive Disorder

Mild neurocognitive disorders, also referred to as mild cognitive impairment (MCI), can be thought of as a middle ground between normal aging and major neurocognitive disorder. Unlike delirium, mild neurocognitive disorders tend to develop slowly and are characterized by a progressive memory loss which may or may not progress to major neurocognitive disorder. Studies have shown that between 5-17% of patients with mild cognitive disorder will progress to major neurocognitive disorder each year. The likelihood of developing mild neurocognitive disorder increases with age, affecting 10-20% of adults ages 65 and older. Men also seem to be at a higher risk of developing mild neurocognitive disorder. In addition to memory loss and cognitive impairment, other symptoms include
aphasia Aphasia is an inability to comprehend or formulate language because of damage to specific brain regions. The major causes are stroke and head trauma; prevalence is hard to determine but aphasia due to stroke is estimated to be 0.1–0.4% in t ...
,
apraxia Apraxia is a motor disorder caused by damage to the brain (specifically the posterior parietal cortex or corpus callosum), which causes difficulty with motor planning to perform tasks or movements. The nature of the damage determines the disor ...
, agnosia, loss of abstract thought, behavioral/personality changes, and impaired judgment.


Major Neurocognitive Disorder

Mild and major neurocognitive disorders are differentiated based on the severity of their symptoms. Also still known as
dementia Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...
, major neurocognitive disorder is characterized by significant cognitive decline and interference with independence, while mild neurocognitive disorder is characterized by moderate cognitive decline and does not interfere with independence. To be diagnosed, it must not be due to delirium or other mental disorder. They are also usually accompanied by another cognitive dysfunction. For non-reversible causes of dementia such as age, the slow decline of memory and cognition is lifelong.


Diagnostic Methods

There are multiple testing methods used to assess a patient's cognition and level of consciousness, including the Mini Mental Status Exam (MMSE), Montreal Cognitive Assessment (MoCA), Mini-Cog, and Cognitive Assessment Method (CAM), Glasgow Coma Score (GCS), Richmond Agitation and Sedation Scale (RASS), etc. The CAM has been shown to be the most commonly used tool to assess for delirium. Additionally, a meta-analysis looking at the accuracy and usefulness of the various testing methods reported that the MMSE was the most commonly used tool to evaluate major neurocognitive disorder, while the MoCA appeared to be the most useful when screening for minor neurocogntive disorder.


Causes


Delirium

There are many causes of delirium, and many times there are multiple factors that can be contributing to delirium, particularly in the hospital setting. Common potential causes of delirium include new or worsening infections (i.e.
urinary tract infection A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidne ...
s, pneumonia, and
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is foll ...
), neurological injury/infections (i.e. stroke and meningitis), environmental factors (i.e. immobilization and sleep deprivation), and medication/drug use (i.e. side effects of new medications, drug interactions, and use/withdrawal from recreational drugs).


Mild and major neurocognitive disorder

Neurocognitive disorders can have numerous causes: genetics, brain trauma, stroke, and heart issues. The main causes are neurodegenerative diseases such as Alzheimer's disease,
Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
, and
Huntington's disease Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an uns ...
because they affect or deteriorate brain functions. Other diseases and conditions that cause NCDs include vascular dementia, frontotemporal degeneration,
Lewy body disease Lewy body dementias are two similar and common subtypes of dementia— dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). Both are characterized by changes in thinking, movement, behavior, and mood. The two conditions have ...
, prion disease, normal pressure hydrocephalus, and dementia/neurocognitive issues due to HIV infection. They may also include dementia due to substance abuse or exposure to toxins. Neurocognitive disorders may also be caused by brain trauma, including concussions and traumatic brain injuries, as well as post-traumatic stress and
alcoholism Alcoholism is, broadly, any drinking of alcohol that results in significant mental or physical health problems. Because there is disagreement on the definition of the word ''alcoholism'', it is not a recognized diagnostic entity. Predomina ...
. This is referred to as
amnesia Amnesia is a deficit in memory caused by brain damage or disease,Gazzaniga, M., Ivry, R., & Mangun, G. (2009) Cognitive Neuroscience: The biology of the mind. New York: W.W. Norton & Company. but it can also be caused temporarily by the use ...
, and is characterized by damage to major memory encoding parts of the brain such as the
hippocampus The hippocampus (via Latin from Greek , ' seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, ...
. Difficulty creating recent term memories is called anterograde amnesia and is caused by damage to the hippocampus part of the brain, which is a major part of the memory process.
Retrograde amnesia In neurology, retrograde amnesia (RA) is a loss of memory-access to events that occurred or information that was learned in the past. It is caused by an injury or the onset of a disease. It tends to negatively affect episodic, autobiographical, ...
is also caused by damage to the hippocampus, but the memories that were encoded or in the process of being encoded in long-term memory are erased


Treatment


Delirium

The overarching principle of delirium treatment is finding and treating the underlying cause. If the patient is truly experiencing delirium, their symptoms should begin improving/resolving with proper treatment of their illness, intoxication, etc. Medication such as
antipsychotic Antipsychotics, also known as neuroleptics, are a class of psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but also in a range o ...
s or
benzodiazepine Benzodiazepines (BZD, BDZ, BZs), sometimes called "benzos", are a class of depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat conditions such as anxiety disorders, ...
s can help reduce the symptoms for some cases. For alcohol or malnourished cases,
vitamin B B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. Though these vitamins share similar names (B1, B2, B3, etc.), they are chemically distinct compounds that often co ...
supplements are recommended and for extreme cases, life-support can be used.


Mild and Major Neurocognitive Disorder

There is no cure for neurocognitive disorder or the diseases that cause it.
Antidepressant Antidepressants are a class of medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common side-effects of antidepressants include dry mouth, weight gain, dizziness ...
s, antipsychotics, and other medications that help slow the progression of memory loss/behavioral symptoms are available and may help to treat the diseases. Ongoing psychotherapy and psychosocial support for patients and families are usually necessary for clear understanding and proper management of the disorder and to maintain a better quality of life for everyone involved; although older patients with major neurocognitive disorders usually require assistance with their daily activities leading to placement in long-term care homes. Speech therapy has been shown to help with language impairment, therefore improving long-term development and academic outcome. Studies suggest that diets with high Omega 3 content, low in saturated fats and sugars, along with regular exercise can increase the level of brain plasticity. Other studies have shown that mental exercise such a newly developed "computerized brain training programs" can also help build and maintain targeted specific areas of the brain. These studies have been very successful for those diagnosed with
schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wi ...
and can improve fluid intelligence, the ability to adapt and deal with new problems or challenges the first time encountered, and in young people, it can still be effective in later life.


See also

* List of cognitive disorders


References

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