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An analysis of 554,312 social media posts and comments found that people discussing narcolepsy and idiopathic hypersomnia often described brain fog through memory problems, forgetfulness and difficulty concentrating. The researchers say the findings suggest patients distinguish brain fog from fatigue and sleepiness, but the self-selected online data cannot establish how common these experiences are across all patients.
A social media analysis of 554,312 posts and comments in online communities for people with narcolepsy and idiopathic hypersomnia found that “brain fog” was commonly associated with memory problems, forgetfulness and difficulty concentrating — not only fatigue. Researchers presented the findings at the Neuroscience Education Institute Fall Congress in Colorado Springs, reporting that the data may help clarify how patients describe a burdensome symptom that has no agreed definition.
The researchers examined posts from two Reddit communities, r/Narcolepsy and r/idiopathichypersomnia, and the Facebook group PWN4PWN. The material covered August 2011 to September 2025, with 85% of the data coming from r/Narcolepsy. The analysis used semantic similarity to identify words and experiences associated with brain fog.
Beyond “forgetfulness,” “memory” and “fatigue,” common associated terms included “drunkenness” and “dissociation.” Terms with strong similarity to brain fog included tiredness, difficulty concentrating, inability to focus, poor memory and memory issues. In a separate grouping of clinical experiences, memory impairment and impaired concentration featured alongside fatigue and forgetfulness.
The team also compared posts according to whether authors emphasized fatigue, sleepiness or both. People describing fatigue and sleepiness at similar levels tended to connect brain fog with memory and focus. In the very sleepiness-dominant group, descriptions more often involved energy and motivation, and included intensity words such as “constant,” “intense” and “severe.”
Why Separating Fog From Fatigue Matters
The findings matter because treating brain fog as another word for tiredness could leave cognitive difficulties out of conversations about how sleep disorders affect daily life. Study presenter Anne Marie Morse, DO, of Geisinger Medical Center, said patients describe effects on school, work, driving and family life, and argued that clinicians should ask about the symptom directly rather than infer it from a sleepiness score.
The analysis does not establish a diagnostic test or show that every patient experiences brain fog in the same way. It does, however, offer patient language that researchers could explore when developing patient-reported measures. Morse said a stable shared vocabulary may help researchers build measures around the experiences patients themselves describe.
For patients and clinicians, the practical point raised by the report is to let people explain what “brain fog” means to them. The researchers’ findings suggest that memory, concentration, energy and motivation can all be part of those accounts, while fatigue or sleepiness may affect how severe the experience feels.
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How the Online Language Developed
The report follows earlier social listening work by Morse and colleagues on the term’s use over time. Morse told MedPage Today that the earlier analysis found “brain fog” predated the COVID-19 pandemic by at least a decade, although use grew afterward alongside research into conditions including celiac disease and fibromyalgia. The current study focused on how people in narcolepsy and idiopathic hypersomnia communities used the phrase without being prompted in a clinical encounter.
In the data, mentions of brain fog rose each year from 2011 to 2017, then remained at about 1% of posts through 2025. The researchers found subtle changes in associated language, including a shift from memory-oriented descriptions toward exhaustion and tiredness between 2011–2017 and 2018–2020. They reported that the meaning remained consistent from 2018 through 2025. These figures describe the posts studied, not the share of patients experiencing the symptom.
““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
The analysis reflects what people chose to post in particular online communities, not a representative sample of everyone with narcolepsy or idiopathic hypersomnia. The authors said self-selection limits generalizability, and that the posts reveal conversational patterns rather than the population prevalence of brain fog. Clinical diagnoses could not be independently verified from social media data.
It is also not clear from this analysis whether brain fog differs reliably between narcolepsy type 1, narcolepsy type 2 and idiopathic hypersomnia. The findings describe associations in language, not the causes of cognitive symptoms or the effect of treatment. The researchers did not establish that the terms used online correspond to a single clinical measure.
Turning Patient Language Into Measures
The report points to further research to test whether patient-described terms can support a reliable outcome measure for brain fog. Any such measure would need validation beyond online posts and would have to account for differences in fatigue, sleepiness and diagnosis. No specific next study or timeline was provided in the source report.
For clinical care, Morse’s stated recommendation is to ask patients what they mean by brain fog and discuss it separately from fatigue or sleepiness. Whether that approach improves assessment or care remains to be tested; the social media analysis identifies a topic for more direct patient and clinical research.
Key Questions
What did the researchers find people meant by “brain fog”?
In the posts analyzed, people often linked brain fog to forgetfulness, memory problems and trouble concentrating. Some also connected it with fatigue, energy or motivation.
Who was included in the analysis?
The researchers analyzed 554,312 posts and comments from two Reddit communities focused on narcolepsy and idiopathic hypersomnia, and the Facebook group PWN4PWN. Most of the data came from r/Narcolepsy.
Does the study show how many patients have brain fog?
No. The study measured language in selected online communities, not the prevalence of brain fog among all people with these disorders. The researchers said the communities were self-selected and the data could not verify diagnoses.
What did the presenter recommend clinicians do?
Morse recommended asking patients to describe brain fog in their own words and treating the response as a symptom in its own right, rather than assuming it means fatigue or sleepiness.
Source: medpagetoday.com
