Neurocognitive Dysfunction

People with ME/CFS experience a range of neurocognitive symptoms.

Cognitive deficits are often the principal disabling feature of ME/CFS. Such deficits restrict the patient’s ability to function, plan, and complete tasks in real world settings.

ME/CFS: A Primer for Clinical Practitioners, IACFS/ME, 2014

Low blood flow to the brain and neuroinflammation exacerbate the cognitive challenges posed by the limited supply of energy in people with ME/CFS.

People can struggle to describe this experience of impaired cognitive function. They may use the words 'brain fog', but this term is not adequate to describe the range and severity of the dysfunction.

Common neurocognitive symptoms


  • short-term memory:
    not creating a memory; inability to retrieve a memory; poor working memory, limiting the capacity to hold information temporarily and using it in reasoning, decision making and carrying out tasks
  • long-term memory:
    inability to retrieve a memory; poor recall of learnt information; inability to transfer new information into long-term memory

Complex cognitive tasks

  • concentration:
    decreased attention span, distractability
  • information processing:
    difficulties in encoding information; slow processing speed; poor ability to categorise; poor mental flexibility
  • perfoming tasks:
    confusion; inability to multitask; discalculia and dyslexia; poor executive function, which affects working memory, mental flexibility, planning and problem solving


  • slowed reaction time when making decisions
  • difficulty making choices and decisions

Communication and social interaction

  • communication difficulties include:
    word retrieval; auditory sequencing; mixing up order of words (linguistic reversal); understanding what is said or written (receptive language); slowed speech; following auditory instructions or taking notes; remembering what one wanted to say or has just said
  • social interaction difficulties include:
    facial recognition; comprehending social cues; working memory and mental flexibility during conversation; emotional lability; verbal disinhibition


  • disorientation, including geographic disorientation; confusion
  • poor spatial and depth perception, contributing to clumsiness

Physical tasks

  • gross motor skills: slowed reaction time; poor balance; lack of coordination; abnormal gait
  • fine motor skills: slurring of speech; difficulties with practical tasks such as writing, eating, grooming
  • muscle weakness: every muscle, voluntary and involuntary, large and small, may be affected

Severity levels

Patients’ perception that simple mental tasks require substantial effort is supported by brain scan studies that indicate greater source activity and more regions of the brain are utilized when processing auditory and spatial cognitive information.

'ME: International Consensus Criteria', Journal of Internal Medicine, 2011

The level of neurocognitive impairment fluctuates and may vary from mild to severe.

For example, it can vary from difficulty with reading long and complex material, through to a complete inability to decipher individual words; it can range from difficulty with word retrieval to a complete inability to speak.

Exertion and neurocognitive dysfunction

  • All neurocognitive impairments worsen with physical or mental exertion, although the worsening of impairment may be delayed (see PEM).
  • A healthy person becomes more alert after exercise. Conversely, people with ME/CFS find their neurocognitive difficulties increase: they become much slower at mental activities; cognitive tasks take extra effort; and muscles weaken and coordination worsens.

It turns out that the ME/CFS brain isn’t less smart than a non-ME/CFS brain, but it’s quite a bit slower, it has trouble processing lots of information, and it takes more energy to think.

Dan Moricoli, Health Rising, 17 Nov 2019


Careful management of rest and activity, known as pacing, will reduce the risk of exacerbating cognitive symptoms. Exceeding the available energy reserve will lead to post-exertional malaise (PEM). The impact of PEM may be delayed and recovery may be prolonged.

People with ME/CFS have low blood flow to the brain, which is exacerbated when posture is upright. Lying down may improve cognitive function.

Neurocognitive Sarah computer in bed

It is important to avoid overload phenomena: sensory overload, multitasking, or attempting to work beyond available energy reserves will increase cognitive dysfunction. Working on one task at a time, in a quiet and calm environment, will maximise available cognitive capacity.

Last edited: 31 August, 2023