A few years ago, I never thought about brain fog—I probably never even used the term. Now, it’s unfortunately no longer just medical jargon; it’s become part of my daily vocabulary. This phenomenon, while long on the radar of healthcare professionals, has been drawing more attention in recent years. But has there actually been an increase in cases, or has brain fog always been a part of our lives and is only now becoming part of our collective consciousness?
Stephen Ferrando, PhD, professor and chair of the Department of Psychiatry and Behavioral Sciences at New York Medical College, has been in practice for 30 years and seen three major waves of brain fog: first, with the rise of research into chronic fatigue syndrome, then “chemo-brain” associated with aggressive cancer treatments, and now, with long COVID. After the onset of the pandemic, it seems the term has stuck: Google searches for “brain fog” skyrocketed, peaking in January 2021. While only a small subset of people used to experience this symptom, now it’s affecting a sizable portion of the population. “COVID has just launched this all into the stratosphere,” says Ferrando.
Brain fog, a subjective experience—is the diminished ability to focus or multitask. “It’s a general kind of slowness and diminishment of acuity, or of the ability to think clearly,” says Ferrando. It feels exactly like it sounds—like a haze has settled over the crown of my head. I just feel off. Like I can’t keep up with the world around me; everything is moving too fast for my sluggish processing.
“Everyone has felt it at some point, even if they haven’t realized it,” says Joel Frank, PsyD, licensed clinical psychologist and neuropsychologist at Duality Psychological Services. “Even when you just have the common cold or flu, your memory is off; you can’t find the words that you really want to say in conversation. You may feel blurry, like after a night of drinking.” But it’s not a condition on its own—it’s a sign that your body is experiencing a shift from homeostasis, he explains. One big reason for that shift in homeostasis? Long COVID.
Ferrando and his team recruited approximately 60 study participants who were part of a long COVID program and performed cognitive skills testing, which involved simple memory tasks. “We found that a more-than-expected subset of those people have neuropsychological test impairment,” he says. “They don’t do as well as the non-COVID-affected population on these tests.” So, when they complain about brain fog, it’s not all in their head. “There is definitely something going on,” he says. A recent study found that this brain fog could be caused by low levels of serotonin, a neurotransmitter that regulates mood and can affect cognitive function, which have been found in long COVID patients.
Anxiety and depression are also major players in brain fog, as anxiety negatively affects working memory, and patients with major depressive disorder are burdened by cognitive symptoms like lack of focus and difficulty with lexical access and decision-making. “Mental illnesses are so taxing on the mind from an emotional and cognitive standpoint that they can produce brain fog,” says Frank. But since 2020, anxiety and depression rates have also risen by at least 25 percent, so it’s a bit of a “chicken and the egg” scenario. Is mental illness or long COVID affecting brain fog more? “That’s the 64 million dollar question,” Ferrando says. It’s a complicated interplay, as severe COVID cases correspond with depression, according to a 2023 study. Those aren’t the only causes of brain fog, though. Medical conditions, like thyroid issues or hormone dysregulation, could lead to brain fog, too, says Frank, as well as nutritional deficiencies, sleep deprivation, medications, and substance use.
