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An analysis of posts in online narcolepsy and idiopathic hypersomnia communities found that brain fog was discussed in connection with memory and concentration problems as well as fatigue or sleepiness. Anne Marie Morse, DO, recommended asking patients to describe the symptom in their own words. Because the data came from social media discussions, the findings do not establish how common these experiences are among people with the disorders.
A social media analysis of 554,312 posts and comments in online narcolepsy and idiopathic hypersomnia communities found that brain fog was discussed in connection with memory problems, difficulty concentrating and forgetfulness, as well as fatigue. The findings were presented at the Neuroscience Education Institute Fall Congress. Anne Marie Morse, DO, recommended asking patients to explain brain fog in their own words rather than translating it into fatigue or sleepiness.
Researchers examined posts from the r/Narcolepsy and r/idiopathichypersomnia subreddits and the PWN4PWN Facebook group, covering August 2011 to September 2025. About 85% of the material came from r/Narcolepsy. The report identified forgetfulness, memory, fatigue, drunkenness and dissociation among the top contextual words associated with brain fog, excluding symptom-relief terms. Other closely related descriptions included difficulty concentrating, inability to focus and poor memory.
The analysis also found differences in how authors discussed brain fog alongside fatigue and sleepiness. Authors in the cohort with a more balanced discussion of those symptoms tended to frame brain fog in terms of memory and focus. Authors in the very sleepiness-dominant cohort more often connected it with energy and motivation and used intensity or duration words such as “constant,” “intense” and “severe.” These patterns describe language in the collected posts, not the rate or severity of symptoms across all people with these disorders.
Mentions of brain fog rose each year from 2011 to 2017, then remained at roughly 1% of posts through 2025, according to the report. Researchers observed a shift in descriptors between the earlier period and 2018–2020, away from memory-focused wording toward exhaustion and tiredness. They reported that the meaning was comparatively consistent from 2018 through 2025.
Why Memory Symptoms Need Separate Questions
The findings suggest that, in the analyzed online discussions, brain fog was not described only in terms of fatigue or sleepiness; some posts also connected it with memory and concentration. Morse recommended that clinicians ask patients what they mean by brain fog rather than assume it means tiredness.
Anne Marie Morse, DO, of Geisinger Medical Center, said patients had told her that cognitive issues cost them their day at school, work, driving and family life. She recommended asking patients to explain brain fog in their own words and treating the response as a symptom in its own right, while recognizing that fatigue or sleepiness may modify its severity. The analysis did not test whether a particular screening approach improves care.
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How Researchers Traced Patient Language
Morse told MedPage Today that “brain fog” lacks an agreed definition and that conversations in clinical or research settings are already conditioned or biased by the setting. The team used social media discussions to learn how people with narcolepsy type 1, narcolepsy type 2 and idiopathic hypersomnia described the phrase on their own, unprompted.
Morse referred to an earlier analysis that found use of the term predated COVID-19 by at least a decade. She also said use grew significantly after COVID-19, alongside research into brain fog across other conditions. In the current analysis, researchers used cosine similarity to calculate semantic similarity. The project was presented at the NEI Fall Congress.
““Brain fog” is one of the most burdensome symptoms people with narcolepsy and idiopathic hypersomnia experience, but there is no agreed definition of what it means.”
— Anne Marie Morse, DO, speaking to MedPage Today
Limits of the Online Sample
The findings cannot establish how prevalent brain fog, memory problems or any other symptom are among people with these diagnoses. The source describes online discussions as reflecting conversational patterns rather than true population prevalence. Most of the material came from one subreddit, which further limits how broadly the results can be generalized.
Researchers also could not independently verify diagnoses from social media posts. The analysis identifies words that appeared in related contexts; it cannot establish causes, clinical severity, or the effects of a treatment. The report describes a possible use of the findings in developing a patient-reported outcome measure, but does not say that such a measure has been created or validated.
From Patient Words to Clinical Measures
The next step proposed by Morse is further research into whether patients’ shared vocabulary can support a patient-reported outcome measure that reflects their experiences. Any measure would need to be developed and tested beyond social media language before its reliability or usefulness in clinical care could be established.
For now, Morse’s recommendation is for clinicians to ask patients directly what brain fog feels like and how it affects their daily lives. The report does not identify a specific follow-up study or publication date, so it remains unclear when researchers may test a formal measure or how it could be incorporated into routine assessment.
Key Questions
What did patients in the analysis mean by brain fog?
In the analyzed posts, brain fog was often associated with memory impairment, forgetfulness and difficulty concentrating. People also connected it with fatigue, tiredness and, in some groups, energy or motivation.
Does the study show that brain fog is separate from fatigue?
The analysis found that people used brain fog in ways that were not limited to fatigue or sleepiness, particularly when describing memory and focus. It does not prove that the experiences are clinically distinct for every patient; fatigue or sleepiness may occur at the same time.
Which conditions did the researchers examine?
The posts came from communities focused on narcolepsy and idiopathic hypersomnia, including discussion of narcolepsy type 1 and type 2. Researchers could not independently confirm individual diagnoses from social media data.
Can these findings show how common brain fog is?
No. The online groups were self-selected, so the posts reflect what members chose to discuss rather than a representative sample. The reported share of posts mentioning brain fog is not an estimate of how many patients experience it.
Source: medpagetoday.com
