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An analysis of more than 554,000 posts from online narcolepsy and idiopathic hypersomnia communities found that people commonly described brain fog through memory problems, difficulty concentrating and forgetfulness. Researchers said the findings suggest patients distinguish it from fatigue or sleepiness, though the self-selected posts cannot establish how common the symptom is among all patients.
A social media analysis of 554,312 posts and comments from online communities for people with narcolepsy and idiopathic hypersomnia found that users most often described brain fog as a problem with memory and concentration, rather than simply as fatigue. The findings, presented at the Neuroscience Education Institute Fall Congress, could inform how researchers measure the symptom and how clinicians ask patients about it.
Researchers examined posts from the Reddit communities r/Narcolepsy and r/idiopathichypersomnia, along with the Facebook group PWN4PWN. The material covered August 2011 to September 2025, and 85% came from r/Narcolepsy. Using semantic similarity analysis, the team identified related words and phrases rather than relying on a definition imposed by researchers.
The most closely associated non-synonymous terms included difficulty concentrating, inability to focus, poor memory and memory issues. Terms describing clinical experiences also centered on impaired memory and concentration, alongside fatigue and forgetfulness. Other frequent contextual words included “drunkenness” and “dissociation”; these are descriptions found in posts, not clinical diagnoses established by the analysis.
The researchers also compared posts in which authors mentioned fatigue, sleepiness, or both. People describing fatigue and sleepiness at similar levels tended to connect brain fog with memory and focus. Those in the very sleepiness-dominant group more often linked it to energy and motivation and used intensity or duration words such as “constant,” “intense” and “severe.” These patterns describe language in the posts and do not establish that the groups experienced distinct medical conditions.
Why Patient Language Matters
The findings offer a patient-generated account of a symptom that researchers say lacks an agreed definition. If people use “brain fog” to describe cognitive difficulties as well as tiredness, treating the phrase as interchangeable with fatigue or sleepiness could miss part of what they are reporting. That distinction matters in settings where symptoms can affect school, work, driving and family life.
Lead researcher Anne Marie Morse, DO, of Geisinger Medical Center, told MedPage Today that clinicians should ask patients what brain fog means to them and treat the answer as a symptom in its own right. She cautioned against translating it automatically into fatigue or sleepiness, while recognizing that those symptoms may occur alongside it or affect its severity.
The analysis may also help researchers develop patient-reported measures using language people already use. Such measures could give future studies a more specific way to ask about cognitive experiences. The study did not test a treatment, establish a diagnostic tool or show how brain fog affects every person with either disorder.
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How Online Descriptions Changed
The report follows earlier social listening work by Morse and colleagues on when people began using the phrase “brain fog.” Morse told MedPage Today that the earlier analysis found the term was in use at least a decade before COVID, with its use growing afterward alongside research across conditions including celiac disease and fibromyalgia. The current analysis focused on how people in narcolepsy and idiopathic hypersomnia communities used the phrase without being prompted in a clinical interview.
In this dataset, mentions of brain fog rose each year from 2011 to 2017, then remained at about 1% of all posts through 2025. Researchers found a shift in descriptors between 2011–2017 and 2018–2020, from memory-related terms toward exhaustion and tiredness. They reported that the vocabulary remained consistent from 2018 through 2025. That stability suggests a shared pattern in these online discussions, but does not prove that all patients define the term the same way.
““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
The results reflect conversations in three selected online communities, not a representative sample of everyone with narcolepsy or idiopathic hypersomnia. The study authors noted that people who post in these groups may differ from patients who do not participate, so the analysis cannot establish the population prevalence of brain fog or of particular symptoms.
Researchers also could not independently verify diagnoses reported in social media posts. The analysis identifies relationships between words in online discussions; it does not show that one symptom causes another, measure clinical severity, or establish that the patterns apply to every person with either condition. The report does not provide a validated patient questionnaire or evidence that using one would improve care.
From Posts to Patient Measures
Morse said the stability of the vocabulary could support development of a patient-reported outcome measure based on patients’ own descriptions. The report does not specify a timeline for creating or validating such a measure. Further research would need to test whether the identified language captures patients’ experiences reliably beyond the online communities studied.
For now, the researchers’ stated practical implication is for clinicians to ask patients directly what they mean by brain fog and how it affects daily activities. Whether that approach changes assessment or treatment outcomes remains untested in this analysis.
Key Questions
What did the analysis find people mean by brain fog?
In the analyzed posts, people commonly connected brain fog with memory problems, difficulty concentrating and forgetfulness. Some also described fatigue, low energy or trouble with motivation.
Was brain fog described as the same thing as fatigue?
No. The researchers found that the term appeared as a distinct concept in the community language, though fatigue and sleepiness sometimes appeared alongside it and could shape how people described it.
Who and what did the study examine?
The analysis covered 554,312 posts and comments from two Reddit communities and one Facebook group focused on narcolepsy and idiopathic hypersomnia, from August 2011 to September 2025.
Can the findings show how common brain fog is among patients?
No. The online communities were self-selected, and the study authors said the data reflect conversational patterns rather than population prevalence. Diagnoses in posts could not be independently verified.
What did the researcher recommend clinicians do?
Morse recommended asking patients to explain brain fog in their own words and not assuming it means fatigue or sleepiness. The analysis did not test whether this approach improves clinical outcomes.
Source: medpagetoday.com
