Major and Mild Neurocognitive Disorders

Learning Objectives

  • Describe and differentiate between major and mild neurocognitive disorders

Abnormal Loss of Cognitive Functioning during Late Adulthood

Neurocognitive disorders (NCDs), previously collectively referred to as dementia, are those that involve impairments in cognitive abilities such as memory, problem-solving, and perception. Dementia is the umbrella category used to describe the general long-term and often gradual decrease in the ability to think and remember that affects a person’s daily functioning. The DSM-5 does not use the term dementia, but instead classifies the decline in cognitive functioning as either a type of major neurocognitive disorder if symptoms are severe, with milder symptoms classified as mild cognitive impairment.

Common symptoms of neurocognitive disorders (NCDs) include emotional problems, difficulties with language, and a decrease in motivation. A person’s consciousness is usually not affected. About 10% of people develop the disorder at some point in their lives, and it becomes more common with age. About 3% of people between the ages of 65 and 74 have a neurocognitive disorder, 19% between 75 and 84, and nearly half of those over 85 years of age. In 2015, neurocognitive disorders (NCDs) resulted in about 1.9 million deaths, up from 0.8 million in 1990. As more people are living longer, neurocognitive disorders are becoming more common in the population as a whole. The DSM-5 has separate classifications for major neurocognitive disorders and mild neurocognitive disorders.

A graphic of a brain being erased by a pencil eraser.

Figure 1. Neurocognitive disorders include changes in cognitive abilities, usually including memory loss.

Neurocognitive disorders generally refer to severely impaired judgment, memory, or problem-solving ability. Neurocognitive disorders can occur before old age and is not an inevitable development even among the very old. Dementia can be caused by numerous diseases and circumstances, all of which result in similar general symptoms of impaired judgment, memory, and problem-solving ability. Alzheimer’s disease is the most common form of neurocognitive disorder and is incurable, but there are also nonorganic causes of neurocognitive disorders that can be prevented. Malnutrition, alcoholism, depression, and mixing medications can also result in symptoms of dementia. If symptoms of dementia causes are properly identified, they can be treated. Cerebral vascular disease can also reduce cognitive functioning.

Smiling old man.

Figure 2. Many people erroneously believe that all elderly people experience dementia, but that is not the case. Neurocognitive disorders caused by conditions such as Alzheimer’s increase significantly with age, but half to two-thirds of the population above age 85 live life without experiencing a neurocognitive disorder.

Major neurocognitive disorder is a syndrome that progresses with significant deterioration of cognitive domains as compared to previous levels of cognitive performance in memory, speech, reasoning, intellectual function, and/or spatiotemporal perception, and may also be associated with changes in emotional behavior and difficulties at the functional level. The cognitive decline is initially noticed by the individual, the family, or the general practitioner/doctor who is usually responsible for the early diagnosis.[1] The cognitive deficits interfere with daily life and require assistance from others to maintain everyday activities. The decline in functioning are not caused by delirium or another mental 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, and Huntington’s disease because they affect or deteriorate brain functions. Other diseases and conditions that cause NDCs include vascular dementia, frontotemporal degeneration, Lewy body disease, prion disease, normal pressure hydrocephalus, and dementia/neurocognitive issues due to HIV infection. These other conditions may also include dementia due to substance abuse or exposure to toxins.

Neurocognitive disorder may also be caused by brain trauma, including concussion and traumatic brain injuries, as well as post-traumatic stress and alcoholism. These examples are referred to as amnesia, and is characterized by damage to major memory encoding parts of the brain such as the hippocampus. 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 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.

Medications as well have an impact on amnesia, especially anti-anxiety drugs. Anterograde amnesia is also associated with anti-anxiety medications, such as lorazepam. Among benzodiazepines, lorazepam has relatively strong amnesic effects, but people soon develop tolerance to this medication with regular use. To avoid amnesia (or excess sedation) being a problem, the initial total daily lorazepam dose should not exceed two mg. Potential side effects of amnesia also apply to use for night sedation. For example, in a sleep study, five participants were prescribed lorazepam four mg at night, and the next evening, three subjects unexpectedly reported memory gaps for parts of that day. After two to three days of treatment, the amnesia effect subsided completely. Amnesic effects cannot be estimated from the degree of sedation present since the two effects are unrelated.

Mild neurocognitive disorder is similar to major neurocognitive disorder, but is characterized by a less extreme cognitive decline in one or more areas, such as attention, memory, language, social cognition, etc. Generally, people with mild neurocognitive disorder can still live independently, but still struggle in some cognitive areas.

In the DSM-5, both major and mild neurocognitive disorders are further specified as to whether it is due to the following causes:

  • Alzheimer’s disease
  • frontotemporal lobar degeneration
  • Lewy body disease
  • vascular disease
  • traumatic brain injury
  • substance/medication use
  • HIV infection
  • prion disease
  • Parkinson’s disease
  • Huntington’s disease
  • another medical condition
  • multiple etiologies
  • unspecified

Try It


dementia: an umbrella category for neurocognitive disorders, characterized by progressive and gradual cognitive deficits due to severe cerebral atrophy

major neurocognitive disorder: deficits in cognitive ability that are acquired (as opposed to developmental), typically represent decline, and may have an underlying brain pathology

mild neurocognitive disorder: neurological disorders involving cognitive impairments beyond those expected based on an individual’s age and education, but which are not significant enough to interfere with instrumental activities of daily living

neurocognitive disorders (NCDs): a category of mental health disorders that primarily affect cognitive abilities including learning, memory, perception, and problem-solving

  1. Sousa S, Teixeira L and Paúl C (2020) Assessment of Major Neurocognitive Disorders in Primary Health Care: Predictors of Individual Risk Factors. Front. Psychol. 11:1413. doi: 10.3389/fpsyg.2020.01413