53 Neurocognitive Disorders

Source of information about DSM diagnoses: American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.). American Psychiatric Publishing.

overview

Neurocognitive disorders (NCDs) are a group of conditions that primarily involve a decline in cognitive abilities. They are acquired, not developmental, meaning they represent a deterioration from a previously higher level of functioning. Cognitive issues are central to these disorders, distinguishing them from mental health conditions where cognitive deficits might be present but aren’t the main feature (like in schizophrenia or bipolar disorder).

The category of NCDs begins with delirium and extends to two key syndromes: major neurocognitive disorder and mild neurocognitive disorder, each with several specific causes, or etiological subtypes.

DSM Chapter Sections:

Delirium: A sudden disturbance in attention and awareness, developing over a short time, often fluctuating throughout the day, and accompanied by changes in cognition or perception.

Other Specified Delirium: Used when a person has delirium symptoms that don’t meet full criteria for delirium but the clinician specifies why (e.g., “substance-induced delirium”).

Unspecified Delirium: Used when delirium symptoms are present, but there’s not enough information to specify the type or cause (e.g., emergency room setting).

Major and Mild Neurocognitive Disorders: Both involve a decline in cognitive abilities, but major NCD is more severe, impacting independence in everyday activities, while mild NCD shows modest cognitive decline with preserved functional independence.

Major or Mild Neurocognitive Disorder Due to Alzheimer’s Disease: A progressive decline in memory and other cognitive functions caused by Alzheimer’s disease, the most common type of NCD.

Major or Mild Frontotemporal Neurocognitive Disorder:
Decline mainly in behavior, personality, or language abilities due to degeneration of the frontal and temporal lobes of the brain.

Major or Mild Neurocognitive Disorder With Lewy Bodies: A disorder characterized by cognitive decline, visual hallucinations, motor symptoms similar to Parkinson’s, and fluctuating alertness, linked to abnormal protein deposits (Lewy bodies).

Major or Mild Vascular Neurocognitive Disorder: Cognitive decline resulting from brain damage due to strokes or other problems with blood vessels in the brain.

Major or Mild Neurocognitive Disorder Due to Traumatic Brain Injury: Cognitive decline caused by a traumatic event to the brain (e.g., blow to the head, concussion), with symptoms depending on the area and severity of injury.

Substance/Medication-Induced Major or Mild Neurocognitive Disorder: Cognitive impairment resulting from the use or withdrawal of substances (like alcohol, drugs, or medications).

Major or Mild Neurocognitive Disorder Due to HIV Infection: Cognitive decline caused by the effects of HIV on the brain’s functioning.

Major or Mild Neurocognitive Disorder Due to Prion Disease: A very rapid cognitive decline caused by rare infectious proteins called prions (e.g., Creutzfeldt-Jakob disease).

Major or Mild Neurocognitive Disorder Due to Parkinson’s Disease: Cognitive decline that occurs in the context of Parkinson’s disease, often after the onset of motor symptoms like tremor and rigidity.

Major or Mild Neurocognitive Disorder Due to Huntington’s Disease:
Cognitive decline caused by Huntington’s disease, a genetic disorder that also leads to motor and psychiatric symptoms.

Major or Mild Neurocognitive Disorder Due to Another Medical Condition: Cognitive impairment attributed to a different identified medical condition (e.g., brain tumor, multiple sclerosis).

Major or Mild Neurocognitive Disorder Due to Multiple Etiologies: Cognitive decline due to more than one cause (e.g., Alzheimer’s disease plus vascular disease).

Major or Mild Neurocognitive Disorder Due to Unknown Etiology: Used when the cause of cognitive decline cannot be determined after evaluation.

Unspecified Neurocognitive Disorder: Reserved for cases where cognitive symptoms are present, but not enough information is available to determine a specific diagnosis.

delirium

Delirium is a sudden and serious disturbance in attention and awareness, causing confusion and difficulty understanding the environment. It develops quickly—over hours or days—and tends to fluctuate in severity, often worsening at night. Delirium is not explained by another preexisting neurocognitive disorder and is usually linked to a medical condition, substance use, medication, or toxin exposure.

Associated Features:

• Disrupted sleep-wake cycle, such as nighttime agitation and daytime drowsiness.

• Emotional instability, including anxiety, fear, anger, euphoria, or apathy.

• Rapid mood swings or unpredictable emotional reactions.

• Vocal outbursts such as calling out, moaning, cursing, or muttering.

• Heightened confusion in low-stimulation environments, especially at night.

Criteria:

A. Disturbance in attention (difficulty focusing, sustaining, or shifting attention) and reduced awareness of surroundings.
B. Develops over a short period (hours to a few days), represents a change from the person’s usual behavior, and fluctuates during the day.
C. Involves an additional cognitive disturbance (e.g., memory issues, disorientation, trouble with language, or distorted perception).
D. The disturbances are not better explained by another neurocognitive disorder or occur during a state of severely reduced alertness like coma.
E. There is clear evidence from the history, physical exam, or lab findings that the disturbance is caused by a medical condition, substance use or withdrawal, medication side effects, toxin exposure, or multiple factors.

Specifiers:

• Acute: Lasts hours to days.

• Persistent: Lasts weeks to months.

• Hyperactive: Agitated, restless, uncooperative behavior.

• Hypoactive: Sluggishness, drowsiness, reduced activity.

• Mixed Activity: Fluctuating between hyperactive and hypoactive states.

• Subtypes: Based on cause, such as substance intoxication, substance withdrawal, medication-induced, medical condition, or multiple causes.

Other Specified Delirium

This category is used when a person shows symptoms similar to delirium that cause significant distress or interfere with social, work, or other important areas of functioning, but the symptoms do not fully meet the criteria for delirium or another specific neurocognitive disorder. Clinicians select this diagnosis when they want to explain why the full criteria are not met. It is recorded as “Other Specified Delirium,” followed by a clear explanation, such as “subsyndromal delirium.”
An example would be a case where the individual presents several signs of delirium but lacks a necessary feature to satisfy the full diagnostic requirements.

Unspecified Delirium

This diagnosis is used when a person shows symptoms that resemble delirium and cause significant distress or impairment in daily functioning but do not meet the full criteria for delirium or another specific neurocognitive disorder. Clinicians use this category when they either do not wish to explain why the criteria are not fully met or when there is not enough information available to make a more precise diagnosis, such as during an emergency room evaluation.

Delirium vs. Dementia vs. Depression

major and mild neurocognitive disorders

Major Neurocognitive Disorder

Major neurocognitive disorder involves a serious decline in cognitive abilities from a previously higher level of functioning. It affects one or more areas like attention, memory, language, executive function, motor skills, or social understanding. The cognitive impairments are substantial enough to interfere with a person’s independence in everyday life, such as needing help with managing finances or medications. The decline cannot be explained by delirium or another mental health condition. Diagnosis includes identifying the underlying cause whenever possible, such as Alzheimer’s disease, traumatic brain injury, or another medical issue.

Criteria:

A. There is clear evidence of significant cognitive decline in one or more cognitive areas, based on both:

1. The individual, someone close to them, or a clinician reporting a notable decline.

2. Objective evidence of substantial impairment, preferably shown through standardized neuropsychological testing or another detailed clinical evaluation.

B. The cognitive deficits interfere with the person’s ability to live independently, meaning they need help with complex daily tasks.
C. The cognitive decline does not occur solely during an episode of delirium.
D. The cognitive deficits are not better explained by another mental disorder, such as major depression or schizophrenia.

Specify if due to:

• Alzheimer’s disease

• Frontotemporal degeneration

• Lewy body disease

• Vascular disease

• Traumatic brain injury

• Substance or medication use

• HIV infection

• Prion disease

• Parkinson’s disease

• Huntington’s disease

• Another medical condition

• Multiple causes

• Unknown cause

Specify current severity:

• Mild: Problems with complex daily activities like housework or managing money

• Moderate: Problems with basic self-care activities like dressing or feeding

• Severe: Complete dependence on others

Specify behavioral features if present:

• With agitation

• With anxiety

• With mood symptoms (like depression, irritability, or euphoria)

• With psychotic symptoms (like delusions or hallucinations)

• With other behavioral issues (like apathy, aggression, disruptive behavior, sleep disturbances)

• Without behavioral or psychological disturbances

mild neurocognitive disorder

Mild neurocognitive disorder involves a modest decline in cognitive abilities, noticeable compared to the person’s prior level of functioning. It affects one or more cognitive areas, such as memory, attention, executive function, language, or social understanding. Despite the decline, individuals maintain their independence in daily activities, though they may need to put in extra effort, use compensatory strategies, or make accommodations. The decline cannot be solely explained by delirium or another mental disorder. Diagnosis includes identifying a possible medical, substance-related, or unknown cause whenever possible.

Criteria:

A. There is evidence of a modest decline in one or more cognitive domains, shown by:

1. Reports of concern from the individual, a knowledgeable informant, or a clinician about cognitive changes

2. Modest impairment on objective testing or another formal clinical evaluation

B. The cognitive deficits do not prevent the person from being independent in daily activities, although they may require extra effort or compensatory strategies.
C. The cognitive decline does not occur solely during a delirium episode.
D. The cognitive changes are not better explained by another mental disorder, such as major depressive disorder or schizophrenia.

Specify whether due to:

• Alzheimer’s disease

• Frontotemporal degeneration

• Lewy body disease

• Vascular disease

• Traumatic brain injury

• Substance or medication use

• HIV infection

• Prion disease

• Parkinson’s disease

• Huntington’s disease

• Another medical condition

• Multiple causes

• Unknown cause

Specify behavioral features:

• Without behavioral disturbance: No significant behavioral changes.

• With behavioral disturbance: Significant behavioral symptoms are present (e.g., anxiety, mood changes, psychosis, apathy).

major or mild neurocognitive disorder due to Alzheimer’s disease

This diagnosis is made when a person meets the criteria for major or mild neurocognitive disorder and shows a gradual and progressive decline in cognitive abilities, typically starting with memory and learning. Alzheimer’s disease usually presents with slow worsening over time without periods of stability. A diagnosis of probable or possible Alzheimer’s disease depends on genetic evidence or the clinical picture. The diagnosis should not be made if another condition better explains the symptoms, such as vascular disease, substance use, or another mental or neurological disorder.

Associated Features:

• Neuropsychiatric symptoms such as agitation, depression, apathy, delusions, and sleep disturbances are common.

• These behavioral and psychological symptoms often appear early, even at the mild NCD stage.

• Symptoms like irritability and depression tend to emerge first, while agitation, combativeness, and hallucinations may develop as the disease progresses.

• In advanced stages, individuals may experience gait disturbances, difficulty swallowing, incontinence, seizures, and muscle jerks (myoclonus).

• Neuropsychiatric symptoms often lead to higher caregiver burden, early institutionalization, and increased mortality.

Criteria:

A. The criteria for major or mild neurocognitive disorder are met.
B. The onset is insidious, and the decline in cognitive abilities is gradual, affecting one or more cognitive domains (at least two for major NCD).
C. Criteria for either probable or possible Alzheimer’s disease are met:

For Major Neurocognitive Disorder:

• Probable Alzheimer’s Disease if either:

  1. Genetic testing or family history shows a causative mutation

  2. Both of the following are present:
     a. Clear decline in memory and learning and at least one other cognitive area
     b. Steady, gradual decline without long periods of stability

• Possible Alzheimer’s Disease is diagnosed if the above are not met.

For Mild Neurocognitive Disorder:

• Probable Alzheimer’s Disease if there is genetic evidence of a causative mutation.

• Possible Alzheimer’s Disease if there is no genetic evidence but both of the following are observed:

  1. Clear decline in memory and learning

  2. Steady, gradual decline without plateaus

D. The cognitive decline is not better explained by other causes such as stroke, substance use, or another neurological or psychiatric condition.

major or mild frontotemporal neurocognitive disorder

Major or mild frontotemporal neurocognitive disorder (NCD) involves a gradual and progressive decline in behavior, personality, or language abilities. It can present in two main forms: a behavioral variant with changes like disinhibition, apathy, or compulsive behaviors, or a language variant with major difficulty in speech production, naming, grammar, or word understanding. Memory and motor skills are usually relatively preserved early on. Diagnosis depends on clinical features and, if available, genetic findings or brain imaging showing frontal or temporal lobe involvement.

Associated Features:

• Movement symptoms (extrapyramidal signs) like rigidity or slowness may occur.

• Features of motor neuron disease, such as muscle weakness or wasting, can appear.

• Some individuals experience visual hallucinations.

• Apathy, poor insight, socially inappropriate behaviors, and emotional blunting are often early signs.

Criteria:

A. The criteria for major or mild neurocognitive disorder are met.
B. Symptoms develop gradually and worsen over time.
C. Either one of the following two forms is present:

1. Behavioral Variant:

• Three or more of these behaviors:

  • Behavioral disinhibition (acting out, lack of restraint)

  • Apathy or loss of motivation

  • Loss of empathy or sympathy

  • Repetitive, compulsive, or ritualistic behaviors

  • Hyperorality (increased eating or changes in food preference)

• Clear decline in social understanding and executive functioning.

2. Language Variant: Major difficulty in language skills, including speech production, naming objects, grammar use, or understanding words.

D. Memory and motor skills are relatively preserved in the early stages.
E. Symptoms are not better explained by a stroke, another type of brain disease, substance use, or another mental, neurological, or systemic disorder.

Probable Frontotemporal Neurocognitive Disorder:

• Diagnosed if there is either genetic evidence (e.g., a known mutation) or imaging showing frontal and/or temporal lobe abnormalities.

Possible Frontotemporal Neurocognitive Disorder:

• Diagnosed if no genetic testing has been done or imaging is not available.

major or mild neurocognitive disorder with Lewy bodies

This disorder involves a progressive decline in cognitive function with early difficulties in attention, executive functioning, and visual perception, rather than memory loss alone. Key features include fluctuating levels of attention and alertness, vivid visual hallucinations, and Parkinsonism (tremors, stiffness) that begins after cognitive symptoms. REM sleep behavior disorder and sensitivity to antipsychotic medications are also important clues. Diagnosis is based on how many core and suggestive features are present and must rule out other causes like stroke, other neurodegenerative diseases, or substance effects.\

Associated Features:

• Frequent falls and episodes of fainting or unresponsiveness.

• Autonomic symptoms like blood pressure drops (orthostatic hypotension), constipation, and urinary incontinence.

• Sleep disturbances such as excessive daytime sleepiness (hypersomnia) and reduced sense of smell (hyposmia).

• High sensitivity to antipsychotic medications, requiring extreme caution if they are used.

Criteria:

A. The criteria for major or mild neurocognitive disorder are met.
B. The symptoms start gradually and progressively worsen over time.
C. The individual meets a combination of core and suggestive features:

Probable NCD With Lewy Bodies:

• Two core features, or

• One core feature plus one or more suggestive features.

Possible NCD With Lewy Bodies:

• One core feature, or

• One or more suggestive features.

Core Diagnostic Features:

1. Fluctuating cognition, with noticeable changes in attention and alertness.

2. Recurrent, detailed visual hallucinations.

3. Spontaneous signs of parkinsonism, developing after cognitive symptoms.

Suggestive Diagnostic Features:

1. Meets criteria for REM sleep behavior disorder (acting out dreams while asleep).

2. Shows severe sensitivity to antipsychotic (neuroleptic) medications.

D. The symptoms are not better explained by another brain disease, mental health disorder, substance use, or medical condition.

major or mild neurocognitive disorder

This diagnosis is used when cognitive decline is mainly caused by problems with blood vessels in the brain. Symptoms typically appear after one or more strokes or due to widespread small vessel disease and mainly affect attention, information processing speed, and executive functioning. The course may be stepwise, with periods of decline followed by stability, or it may be gradual. Diagnosis is supported by clinical history, neurological exams, and often brain imaging showing vascular damage. Other causes must be ruled out.

Associated Features:

• History of strokes or transient ischemic attacks (mini-strokes).

• Physical signs such as weakness on one side of the body, speech difficulties, or visual field loss.

• Personality changes, emotional instability, depression, or lack of motivation (abulia).

• Vascular depression: late-onset depression with slowed thinking and impaired executive function linked to small vessel disease.

Criteria: 

A. The individual meets the criteria for major or mild neurocognitive disorder.
B. The cognitive decline is consistent with vascular causes, shown by either:

1. Symptoms appearing after one or more strokes.

2. Cognitive deficits, especially in complex attention and executive functions.

C. There is medical, physical exam, or neuroimaging evidence of significant cerebrovascular disease accounting for the symptoms.
D. The symptoms are not better explained by another brain disease or medical condition.

Probable Vascular Neurocognitive Disorder:

• Neuroimaging shows significant vascular damage.

• Symptoms appear soon after a documented stroke.

• There is strong clinical and genetic evidence for a vascular cause.

Possible Vascular Neurocognitive Disorder:

• Diagnosis is made when only some supporting evidence is available or neuroimaging has not been completed.

major or mild neurocognitive disorder due to traumatic brain injury

This disorder describes lasting cognitive impairment resulting from a traumatic brain injury (TBI). TBI is caused by an external force impacting the head or brain, leading to immediate effects like loss of consciousness, memory gaps, disorientation, or neurological symptoms. The cognitive disorder must begin right after the injury (or after regaining consciousness) and continue beyond the early recovery period. Common cognitive issues include problems with attention, memory, processing speed, executive function, and sometimes social skills.

Associated Features:

• Subtle neurological signs, such as primitive reflexes (e.g., snout or palmomental reflexes).

• Eye movement abnormalities (issues with saccades or smooth-pursuit).

• Problems with complex attention, memory retrieval, or executive functioning.

• Posttraumatic epilepsy linked to specific brain areas, potentially matching the type of cognitive deficit (e.g., temporal lobe seizures affecting memory).

Criteria:

A. The criteria for major or mild neurocognitive disorder are met.
B. There is clear evidence of a traumatic brain injury, involving at least one of the following:

1. Loss of consciousness.

2. Posttraumatic amnesia (memory loss surrounding the injury).

3. Disorientation and confusion immediately after the injury.

4. Observable neurological signs (e.g., imaging showing brain injury, visual field loss, weakness, sensory loss, language disturbances).

C. The neurocognitive disorder must start immediately after the injury or after recovering consciousness and must persist beyond the acute recovery phase.

Substance/medication-induced major or mild neurocognitive disorder

This diagnosis is made when lasting cognitive impairments develop due to substance or medication use. The cognitive problems must persist beyond normal intoxication or withdrawal periods and must not occur exclusively during delirium. The substance must be known to be capable of causing these impairments, and the timeline of use and symptoms must match. Different substances can cause specific patterns of cognitive difficulties, and the diagnosis must rule out other medical or psychiatric causes.

Associated Features:

• Smell of inhalants on breath or rash around the nose/mouth from “huffing.”

• Workers exposed to solvents may develop symptoms.

• Central nervous system depressants (e.g., alcohol, sedatives) can cause added irritability, anxiety, sleep issues, and sadness.

• Stimulant-induced NCD may cause depression, excessive sleepiness, and apathy after use.

• Severe alcohol-related NCDs can include motor problems like poor coordination, balance issues, and emotional instability.

• Long-term damage can lead to aggression, apathy, or inappropriate affect.

Criteria:

A. The individual meets the criteria for major or mild neurocognitive disorder.
B. The cognitive impairments continue beyond the expected time of intoxication or withdrawal and do not occur only during delirium.
C. The substance or medication used must be capable of causing the observed cognitive deficits.
D. The timeline of substance use and the development of cognitive problems must match, and deficits should improve or stabilize with abstinence.
E. The cognitive deficits are not better explained by another medical condition or mental disorder.

Specify if:

• Persistent: If impairments continue significantly even after a long period of abstinence.

major or minor neurocognitive disorder due to hiv infection

This diagnosis applies when a person with documented HIV infection develops lasting cognitive impairments that cannot be better explained by other brain diseases, medical conditions, or mental disorders. The cognitive decline often follows a “subcortical pattern,” meaning it mainly affects executive functioning, processing speed, attention, and learning new information, while basic memory recall remains more preserved. It reflects the direct or indirect effects of HIV infection in the brain.

Associated Features:

• Higher risk in older adults, women, and individuals with lower education levels.

• Increased likelihood with comorbid conditions like depression, substance use disorders, diabetes, or hypertension.

• Higher risk linked to history of severe immune suppression, high cerebrospinal fluid (CSF) viral loads, and elevated inflammatory markers (e.g., TNF-α, IL-6, C-reactive protein).

• In advanced cases, neuromotor symptoms like severe clumsiness, balance issues, and motor slowing may appear and worsen over time.

Criteria:

A. The individual meets the criteria for major or mild neurocognitive disorder.
B. There is confirmed infection with HIV.
C. The cognitive decline is not better explained by non-HIV-related brain conditions, such as opportunistic infections (e.g., progressive multifocal leukoencephalopathy, cryptococcal meningitis).
D. The cognitive symptoms are not better explained by another medical condition or mental disorder.

major or mild neurocognitive disorder due to prion disease

This disorder refers to a cognitive decline caused by prion diseases, which are rare, rapidly progressing brain conditions. These diseases include types like Creutzfeldt-Jakob disease and are caused by abnormal proteins known as prions. Symptoms often start subtly but worsen quickly, usually leading to significant cognitive and motor impairments. Most individuals develop the major form of the disorder due to its fast progression, though some may initially show milder symptoms.

Criteria:

A. The individual meets the criteria for major or mild neurocognitive disorder.
B. The condition begins subtly, and the decline usually happens quickly.
C. There are motor symptoms linked to prion disease, such as muscle jerks (myoclonus) or uncoordinated movements (ataxia), or there is supportive biomarker evidence.
D. The condition is not caused by another medical condition or mental disorder

major or mild neurocognitive disorder due to parkinson’s disease

This disorder involves a cognitive decline that develops in individuals who already have a diagnosis of Parkinson’s disease. It progresses slowly and may vary in severity over time. The decline typically begins after the onset of motor symptoms, and may involve problems with memory, attention, or decision-making. The diagnosis is more certain when no other condition is likely causing the symptoms and Parkinson’s disease clearly comes first.

Associated Features:

• Apathy

• Depressed or anxious mood

• Hallucinations or delusions

• Personality changes

• REM sleep behavior disorder

• Excessive daytime sleepiness

• Freezing of gait and falls

• Early bilateral symptoms

• Postural instability and gait disturbance (PIGD subtype)

• Reduced sense of smell (hyposmia)

Criteria:

A. The individual meets criteria for either major or mild neurocognitive disorder.
B. The cognitive issues occur in the context of an existing diagnosis of Parkinson’s disease.
C. The decline starts gradually and progresses slowly.
D. The symptoms are not due to another medical or mental health condition.

For a diagnosis of “probably due to Parkinson’s disease,” both of the following must be true:

1. There is no indication of another possible cause for the decline.

2. Parkinson’s disease started before the cognitive symptoms.

If only one of the two conditions above is met, the diagnosis is considered “possibly due to Parkinson’s disease.”

major or mild neurocognitive disorder due to Huntington’s disease

Major or mild neurocognitive disorder due to Huntington’s disease involves a gradual decline in cognitive abilities due to Huntington’s disease, a genetic condition that affects the brain. Early cognitive changes often impact planning, organizing, and decision-making more than memory. These mental symptoms may appear before the well-known movement problems like involuntary jerks or slowed movements. The diagnosis requires either confirmation of Huntington’s disease through motor symptoms and family history, genetic evidence, or a strong risk based on family history or genetic testing.

Associated Features:

• Irritability

• Apathy

• Anxiety

• Obsessive-compulsive symptoms

• Depression

• Less commonly, psychosis

Criteria:

A. The person meets the criteria for major or mild neurocognitive disorder.
B. The symptoms begin gradually and worsen over time.
C. The person has a confirmed diagnosis of Huntington’s disease or is at risk based on family history or genetic testing.
D. The condition is not due to another medical or mental health condition.

major or mild neurocognitive disorder due to another medical condition

This diagnosis applies when a person develops cognitive decline as a direct result of a medical condition not covered under specific other categories, such as Alzheimer’s disease. It is essential that medical evaluation shows a clear link between the condition and the cognitive impairment. Examples include brain tumors, endocrine imbalances, severe infections, and autoimmune diseases. Identifying and treating the underlying condition may improve or stabilize the symptoms.

Criteria:

A. The person meets the criteria for either major or mild neurocognitive disorder.
B. There is evidence from medical history, physical exam, or lab findings that the cognitive symptoms are caused by another medical condition.
C. The cognitive symptoms are not better explained by another mental disorder or by a more specific neurocognitive disorder diagnosis.

major or mild neurocognitive disorder due to multiple etiologies

This diagnosis applies when cognitive decline results from more than one medical condition. For example, a person might have both Alzheimer’s disease and vascular brain changes that together cause neurocognitive symptoms. The contributing conditions must be confirmed through history, physical exams, or lab tests. This diagnosis helps capture complex cases where no single cause fully explains the impairment.

Criteria:

A. The person meets the criteria for either major or mild neurocognitive disorder.
B. There is clear evidence that more than one medical condition is contributing to the disorder, based on medical history, physical exam, or lab tests.
C. The symptoms are not better explained by another mental disorder and are not only present during delirium.

Major or Mild Neurocognitive Disorder Due to Unknown Etiology

This diagnosis is used when a person has significant cognitive decline, and there is some indication of a medical cause, a combination of causes, or possibly substance use, but there is not enough clear evidence to pinpoint a specific source. This category acknowledges the limitations of current medical knowledge or diagnostic information in certain complex cases.

Criteria:

A. The person meets the criteria for either major or mild neurocognitive disorder.
B. There is some evidence from history, physical examination, or lab results suggesting a medical cause, a combination of causes, or a mix of medical issues and substance use, but a specific cause cannot be confirmed.
C. The symptoms are not better explained by another mental disorder, are not caused solely by substance use, and do not occur only during delirium.

Unspecified Neurocognitive Disorder

This diagnosis is used when a person shows symptoms that resemble a neurocognitive disorder and these symptoms cause meaningful distress or impair daily functioning, but the full criteria for any specific neurocognitive disorder are not met.

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