Brain fog describes the inability to think or concentrate when we are sick. We don’t notice it as much when we have a bad cold or the flu, because we don’t even try to go to work or school for the few days that it lasts, and then it goes away. But in chronic illness, lasting weeks, months, or years, it begins to interfere with our ability to do our job, pay our bills, pass our courses or maintain our relationships. Brain fog is experienced by people with autoimmune and inflammatory conditions, such as multiple sclerosis, rheumatoid arthritis, lupus, fibromyalgia and chronic fatigue syndrome, and chronic or post-infectious conditions such as Lyme disease. People undergoing chemotherapy often suffer from “chemo-brain.” Brain fog has been poorly recognized and understood in the past, but has come under closer study since the recent surge of “long COVID.” 

Brain fog often varies in severity along with other symptoms. It is caused by some aspect of immune system activation that we don’t yet fully understand, perhaps involving cytokines, the chemicals that instruct white blood cells to attack invading bacteria. (A more technical term for brain fog would be immune-mediated cognitive dysfunction.) I think of it as “the brain on power saver.” In the same way that we lose our energy, and our appetite, the immune system may be conserving energy by shutting down non-essential functions, in order to better fight infection.  Unfortunately, although higher-level brain function may be considered non-essential by the immune system, focusing, remembering and getting things done seem pretty important to us.

We all have times when we are thinking less clearly or forgetting something we should remember, and these usually are times of stress or fatigue. We get foggy-headed when we have a cold, for example, and even if we drag ourselves to work or school, not much gets accomplished. We try to read something late at night, and our eyes get to the bottom of the page, but we have no idea what we’ve read.  Just as the higher level processes of thinking and attention only work when we are safe and our basic needs are met (Affective System), they don’t work well when we are sick or fatigued, or when we are worried or upset about something. Because we have all had these brief experiences of brain malfunction, we tend to become concerned only when they persist over time. 

Treatment & Accommodations

Treatment for brain fog parallels treatment for the underlying condition. In addition, it is important to reduce your expectations for productivity when experiencing brain fog, so you do not increase your stress level, which we know worsens symptoms and hampers recovery, along with making us generally more miserable. Cognitive limitations accompanying illness (including mental illness) must, by law, be accommodated by employers and educational institutions. (See my article on Educational Accommodations for Children with Lyme Disease)