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A social media analysis of more than 554,000 posts and comments from narcolepsy and idiopathic hypersomnia communities found that people often described brain fog through memory problems and difficulty concentrating. Researchers say the findings distinguish it from fatigue or sleepiness, though self-selected online posts cannot establish how common these experiences are 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 “brain fog” was commonly described through memory problems and difficulty concentrating, rather than as another word for fatigue alone. The findings, presented by Anne Marie Morse, DO, and colleagues at the NEI Fall Congress, suggest clinicians may need to ask about the symptom separately from sleepiness.
The researchers examined posts from the r/Narcolepsy and r/idiopathichypersomnia subreddits and the PWN4PWN Facebook group, covering August 2011 through September 2025. About 85% of the material came from r/Narcolepsy. The team used semantic similarity analysis to identify words and phrases that appeared in contexts similar to “brain fog.”
Among the most closely associated terms were tiredness, difficulty concentrating, inability to focus, poor memory and memory issues. Other frequent descriptions included forgetfulness, fatigue, drunkenness and dissociation. Words appearing in discussions of relief included “clears,” “lifted” and “clearing.” These are patterns in community posts, not clinical measurements or estimates of how many patients experience each symptom.
The researchers also compared posts by whether authors emphasized fatigue, sleepiness or both. People whose posts were balanced between fatigue and sleepiness more often linked brain fog to memory and focus. Those in the very sleepiness-dominant group more often connected it with energy and motivation, and used intensity or duration terms such as “constant,” “intense” and “severe.”
Why Separate Brain Fog From Sleepiness
The findings matter because a broad label such as fatigue may miss the cognitive difficulties patients are trying to describe. Memory and concentration problems can affect school, work, driving and family life, Morse said. If clinicians assume brain fog is simply sleepiness, they may not ask about those effects directly.
The analysis does not show that brain fog is a distinct biological condition or establish a diagnostic test. It does offer evidence that people in these communities use the term to describe experiences that overlap with, but are not always identical to, fatigue and sleepiness. Researchers said that shared language could help inform future patient-reported measures, if further work supports it.
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How Researchers Tracked Patient Language
Morse told MedPage Today that there is no agreed definition of brain fog, including whether people with different conditions mean the same thing by it. She said clinical encounters can shape how patients discuss symptoms, prompting the team to examine descriptions shared online without a researcher’s question guiding the response.
The report also notes that the phrase predates the COVID-19 pandemic by at least a decade, based on the researchers’ earlier social listening analysis. In the current dataset, brain fog mentions rose annually from 2011 to 2017, then remained at about 1% of posts through 2025. The team found a shift in associated descriptions between 2011–2017 and 2018–2020, from memory-focused language toward exhaustion and tiredness; meanings were more consistent from 2018 through 2025.
““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, of Geisinger Medical Center, speaking to MedPage Today
Limits of the Online Evidence
The dataset reflects self-selected online communities, not a representative sample of everyone with narcolepsy or idiopathic hypersomnia. The researchers cautioned that conversational patterns cannot establish symptom prevalence, and diagnoses reported in social media posts could not be independently verified. Most of the material came from one subreddit, which may also shape the language captured.
The analysis identifies associations between words, but it cannot determine what causes brain fog, how severe it is for individual patients or whether the same descriptions apply across diagnoses and clinical settings. It also does not establish that a patient-reported measure based on these terms would improve diagnosis or care.
From Community Terms to Clinical Measures
The findings were presented at the NEI Fall Congress; the source report does not describe a specific next study or timeline. Researchers say the consistency of descriptions over several years may support future work on a patient-reported outcome measure built around patients’ own language. That would require additional testing beyond this social media analysis.
For now, Morse recommends that clinicians ask patients to describe brain fog in their own words and discuss its effects separately from fatigue or sleepiness. Whether that approach leads to better measurement or care remains to be tested.
Key Questions
What did the analysis find people mean by brain fog?
Posts often associated it with memory impairment, forgetfulness and trouble concentrating. Some also linked it to tiredness, fatigue, energy or motivation.
Does the study show how common brain fog is among patients?
No. The analysis counted and compared language in online posts; it did not measure prevalence among all people with narcolepsy or idiopathic hypersomnia.
Which groups and time period were included?
Researchers analyzed two Reddit communities and the PWN4PWN Facebook group, with posts and comments dated from August 2011 to September 2025. About 85% came from r/Narcolepsy.
What did the researcher recommend clinicians do?
Morse recommended asking patients to explain brain fog in their own words and treating it as a symptom to discuss separately, while recognizing that fatigue or sleepiness can occur alongside it.
Source: medpagetoday.com
