Brain Fog Test (BFS)

"Brain fog" is an everyday description rather than a formal medical diagnosis, capturing a familiar cluster of complaints: feeling mentally drained, struggling to recall common words, losing focus, and experiencing sluggish thoughts. Although people often report feeling foggy after poor sleep, a stressful stretch, or an illness, the term had no agreed definition and no validated measure. To address this gap, Agata Debowska, Daniel Boduszek, and their colleagues at SWPS University developed the Brain Fog Scale (BFS) in 2024. Drawing on the clinical literature and a panel of ten psychologists and medical doctors, they defined brain fog as a cognitive dysfunction marked by problems with concentration and memory, inattention, confusion, difficulty understanding spoken and written language, reduced mental sharpness, and mental fatigue, and cut an initial pool of 30 statements to 23.

The BFS organizes these complaints into three closely related dimensions. The first, Mental Fatigue, assesses sluggish thinking, daytime sleepiness, irritability, distractibility, and feeling mentally exhausted or drained. The second, Impaired Cognitive Acuity, captures lapses in mental sharpness, including difficulty concentrating, trouble taking in new information, struggling to find words, and feeling as though your mind has gone blank. The third, Confusion, reflects disorientation and detachment, such as feeling spaced out, daydreaming, losing your train of thought, or having trouble understanding what others are saying. While absent-mindedness scales measure a long-standing tendency toward everyday slips, such as forgetting why you walked into a room, the BFS captures how clouded and fatigued your thinking has felt over the last two weeks.

In their 2024 study of 1,452 Polish university students, Debowska and colleagues found that students who had tested positive for COVID-19 scored markedly higher on all three subscales than matched peers who never had. In a 2026 study of 2,005 U.S. adults chosen to mirror the population by sex, age, and ethnicity, higher BFS scores were moderately to strongly linked with psychological distress, stress, physical fatigue, and sleep problems, and with poorer self-rated health. Women, younger adults, and people regularly taking pain or sleep medication averaged higher scores, while people with high levels of physical activity scored lower. These are associations from surveys, not proof of what causes brain fog.

Your results combine these areas into a Total Brain Fog score alongside individual scores for Mental Fatigue, Impaired Cognitive Acuity, and Confusion. The mark across each band of your chart is that area's published average from the 2026 survey of 2,005 U.S. adults by Debowska and colleagues, rescaled to a 0 to 100 range, and your result sentence compares your Total Brain Fog with the survey's average. The published scale asks how often you have had each experience, while this test asks how much you agree, so these averages are approximate estimates rather than validated percentiles. Because everyday mental sharpness shifts with rest, illness, and workload, your scores are a snapshot of the last two weeks rather than a measure of your intelligence or memory.

This test is provided for educational and self-reflection purposes only and is not a diagnostic tool or a substitute for professional medical care. Brain fog can stem from numerous overlapping factors, ranging from routine exhaustion and nutritional deficits to underlying medical conditions, and no online screening can identify a specific cause. This assessment is based on the Brain Fog Scale (BFS) published by Debowska et al. but is not affiliated with or endorsed by the original authors or SWPS University. If you find that cloudy thinking, memory problems, or persistent fatigue interfere with your daily responsibilities, consider discussing your symptoms with a qualified healthcare professional.

References

• Debowska, A., Boduszek, D., Ochman, M., Hrapkowicz, T., Gaweda, M., Pondel, A., & Horeczy, B. (2024). Brain Fog Scale (BFS): Scale development and validation. Personality and Individual Differences, 216, 112427.
• Debowska, A., Boduszek, D., Bielak, S., Hales, G. K., & Bojnowska, U. (2026). Validation and standardization of the Brain Fog Scale (BFS) in the U.S. general population. Personality and Individual Differences, 249, 113499.

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