How’s the weather inside your head? If it’s foggy, you are not alone. You may have what people with a variety of health conditions call brain fog — a common term for thinking problems that can make getting through the day a mental slog.
While there’s no official list of symptoms, people with brain fog often say that “their thinking is not clear, it’s cloudy,” says Lynne Shinto, a naturopathic doctor and professor of neurology at Oregon Health & Science University. “They might say, ‘I have problems concentrating.… I feel like I don’t have clarity of thought, and sometimes I forget things.’ ”
Unlike people with dementia or other, more severe cognitive challenges, they often can do what they need to do in a day, but “their thought processes are just slower,” she says.
Cognitive psychologist Julie Dumas, a professor of psychiatry at the University of Vermont, says brain fog can be like “thinking through mud or molasses.”
Brain fog is not a disease or disorder itself, so it’s important to figure out the underlying cause, Dumas says.
A recent research review published in Trends in Neurosciences found that brain fog has been linked with more than a dozen chronic conditions, and exact symptoms and cognitive test results can vary, depending on the apparent cause. That suggests that there’s no one underlying pathway, the researchers said.
Here are some of the most common possible causes of brain fog:
1. Sleep problems
Not getting enough sleep is a major cause of brain fog. If you have chronic insomnia, which can include problems falling or staying asleep, improving your sleep can clear the fog, says Leslie Swanson, a clinical associate professor of psychiatry at Michigan Medicine.
Another sleep disorder strongly tied to daytime sleepiness and foggy thinking is obstructive sleep apnea, a disorder in which people stop breathing repeatedly during sleep. Many people go undiagnosed and untreated for this condition, Swanson says. “Snoring is a red alert” and a good reason to see a doctor.
2. Perimenopause
Women going through the hormonal shifts of perimenopause, the years before periods end, often report brain fog, with problems like forgetting names or having trouble focusing at work, Swanson says. Studies back them up, she says, finding “small declines” in learning and verbal memory.
Part of the explanation is that perimenopause often comes with sleep disturbances, especially unwanted awakenings during the night, Swanson says. Hot flashes cause some, but not all, of those disturbances, she says.
Hormonal shifts may affect sleep and brain functioning even in women who don’t have a lot of hot flashes, she says. The good news, she says, is that the fog tends to lift after menopause.
3. COVID-19 and other infections
When you get the flu, COVID-19 or any infection, especially with a fever, you can get brain fog, which is likely linked to inflammation, Dumas says. But one reason more people are hearing about brain fog these days is that it’s a common part of long COVID, the symptoms that continue or develop after the initial illness, she says.
Shinto says she has seen some long COVID patients with “intense brain fog, where they have a lot of trouble concentrating [and] intense mental tasks are very draining.”
In addition, many are constantly physically exhausted. That combination, along with other symptoms, can be disabling, making it impossible for some people to manage their usual daily activities, she adds.