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A social media analysis of 554,312 posts and comments from narcolepsy and idiopathic hypersomnia communities found that people often described brain fog through memory problems, difficulty concentrating and forgetfulness. The researchers said the term appeared distinct from fatigue and sleepiness, though the self-selected online data cannot establish how common these experiences are among all patients.
An analysis of 554,312 posts and comments in online communities for people with narcolepsy and idiopathic hypersomnia found that members commonly used “brain fog” to describe memory problems and difficulty concentrating, not only tiredness. The findings, presented at the Neuroscience Education Institute Fall Congress, suggest the term may capture a distinct patient-reported experience, although social media posts cannot establish how broadly the pattern applies to patients overall.
Researchers examined posts from two Reddit communities, r/Narcolepsy and r/idiopathichypersomnia, and the Facebook group PWN4PWN, 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 appearing in contexts related to brain fog.
Among the terms most closely associated with brain fog were “forgetfulness,” “memory,” “fatigue,” “drunkenness” and “dissociation.” Other terms identified by the analysis included “difficulty concentrating,” “inability to focus,” “poor memory” and “memory issues.” The authors also grouped descriptions of clinical experiences: memory impairment and dysfunction, impaired concentration, fatigue and forgetfulness featured prominently.
Some words appeared in posts about brain fog lifting or improving, including “clears,” “lifted,” “lifts” and “clearing.” The study also compared people’s descriptions across groups categorized by whether they discussed fatigue, sleepiness, or both. The researchers reported the largest difference between the balanced fatigue-and-sleepiness group and a group in which sleepiness exceeded fatigue by at least 7.5%.
Why Brain Fog May Need Its Own Measure
The findings matter because clinicians and researchers do not have an agreed definition of brain fog in narcolepsy and idiopathic hypersomnia. If patients use the phrase to describe memory and focus problems as well as low energy, treating it as a synonym for fatigue or sleepiness could miss part of what they report.
Study lead Anne Marie Morse, DO, of Geisinger Medical Center, said the consistent language in the online communities could help researchers develop a patient-reported outcome measure based on patients’ own descriptions. Such a measure could give future research a way to track cognitive symptoms directly. The analysis does not itself validate a new measure or show that any particular treatment improves brain fog.
The reported problems can affect daily activities, including school, work, driving and family life, Morse said. The study did not measure those effects directly; it analyzed language in community posts. Its findings point to a reason for clinicians to ask patients what they mean by brain fog rather than infer it from a sleepiness score alone.
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How Patients’ Language Was Analyzed
Morse told MedPage Today that earlier research and clinical conversations can shape how people define brain fog. The research team therefore examined unprompted discussions in online communities, aiming to learn how people with narcolepsy type 1, narcolepsy type 2 and idiopathic hypersomnia described the term in their own words.
The researchers reported that mentions of brain fog rose each year from 2011 to 2017, then remained at about 1% of all posts through 2025. They described changes in associated language as subtle. From 2011 to 2017 compared with 2018 to 2020, descriptions shifted somewhat away from memory-focused words toward exhaustion and tiredness; the analysis found the meaning remained consistent from 2018 through 2025.
Morse also said a prior social listening analysis found use of “brain fog” predating the COVID-19 pandemic by at least a decade, with use growing afterward. The current analysis focused on how people in sleep-disorder communities used the phrase, rather than establishing when the term first emerged or why its use changed.
““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 Online Patient Reports
The analysis describes language used in selected online groups, not the prevalence of brain fog or particular symptoms among all people with narcolepsy or idiopathic hypersomnia. The researchers cautioned that online communities are self-selected and reflect conversational patterns. They also could not independently verify members’ clinical diagnoses from social media data.
The study does not establish why individual members used a particular phrase, whether the same wording means the same thing to every person, or how the descriptions relate to clinical tests or symptom severity. The large number of posts does not remove those limitations, and the heavy contribution from one Reddit community may affect how representative the overall findings are.
Questions for Clinics and Future Research
The findings were presented at the NEI Fall Congress; the supplied report does not describe a scheduled follow-up study or a validated brain-fog assessment tool. A next research step would be to test whether patient-derived questions can reliably capture memory, concentration and other experiences across different patient groups and clinical settings.
For now, Morse advised clinicians to ask patients directly what they mean by brain fog and to record it separately from fatigue or sleepiness. Whether the reported vocabulary can be turned into a reliable clinical measure, and whether patterns differ across diagnoses, remains to be tested.
Key Questions
What did the social media analysis find about brain fog?
In 554,312 posts and comments from online narcolepsy and idiopathic hypersomnia communities, brain fog was frequently associated with memory problems, forgetfulness and difficulty concentrating, as well as fatigue.
Does the study show that brain fog is the same for every patient?
No. The analysis describes patterns in community posts; it does not show that every patient experiences or defines brain fog in the same way. The authors also could not independently confirm users’ diagnoses.
Was brain fog described only as tiredness?
No. Fatigue and sleepiness appeared in the analysis, but memory and concentration terms were also prominent. Lead researcher Anne Marie Morse said patients’ descriptions suggest brain fog should not automatically be treated as another name for fatigue or sleepiness.
What should clinicians take from the findings?
Morse recommended asking patients to explain brain fog in their own words and treating the response as a distinct symptom in the conversation. The study does not establish a specific diagnostic test or treatment for brain fog.
Source: medpagetoday.com
