Brain fog is not a medical term or diagnosis but rather a commonly used phrase that describes a constellation of symptoms. It generally is caused by systemic conditions affecting the brain (conditions that exist outside the brain that affect how it functions) and can include a wide variety of symptoms. These may include poor concentration, memory, and mental clarity; mild confusion; difficulty focusing and finding words; mental fatigue; slowed cognitive processing; and problems with task planning.
Several neurologic conditions, including migraine, Parkinson's disease, stroke, and dementia, can cause brain fog. It also may occur with conditions affecting the autonomic nervous system, including postural orthostatic tachycardia syndrome (POTS) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
Other causes include stress or mood conditions, such as anxiety and depression, as well as hormonal conditions and fluctuations like those people may experience during pregnancy, menopause, and menstruation, and with thyroid disorders. Autoimmune diseases, such as multiple sclerosis and lupus; chemotherapy, sedatives, and other therapies affecting the central nervous system; and alcohol or substance disorders also may play a role. People may experience brain fog if they have sleep-related problems, such as sleep apnea, sleep deprivation, and shift work that causes sleep disruptions, or electrolyte disturbances, such as extremely high or low blood sugar levels.
Brain fog also is one of the most common symptoms of long COVID, a chronic condition in which people continue to experience health problems for at least three months after their initial infection with COVID-19. A large proportion of those patients also have ME/CFS and/or POTS. We suspect that patients have dysfunction in their blood-brain barrier (the membrane that separates a person's blood from their brain tissue), dysregulation of vessels in their brain, and/or dysregulation of their immune system.
To treat brain fog, we try to assess the contributing factors. Then we treat the underlying issue, which could include conditions such as obstructive sleep apnea, migraine, menopause, or attention deficit hyperactivity disorder (ADHD). For instance, patients may start using a continuous positive airway pressure (CPAP) machine or the stimulant modafinil if they have sleep apnea, take calcitonin gene-related peptide inhibitors for migraine, or take the medication guanfacine or other stimulants for ADHD.
After this, we reassess the patient. If they still have brain fog despite these treatments, we would try others specifically aimed at the brain fog. Making certain lifestyle changes can reduce the duration and severity of brain fog, too, such as getting seven to eight hours of minimally interrupted sleep each night and treating sleep conditions. We advise patients to stay hydrated and eat well-rounded, nutritious meals in addition to doing regular aerobic (cardio) and anaerobic (resistance training) exercises if medically cleared to do so. We also tell them to avoid excessively using alcohol and other substances.
Treating mood conditions proactively with psychotherapy and pharmacotherapy, if needed, and proactively managing a patient's stress can help as well. We may prescribe medications such as guanfacine, stimulants like modafinil, or activating mood medications like bupropion (Wellbutrin) to treat brain fog.
People should reach out to their doctors when brain fog symptoms impact their daily function and life. If they suddenly feel confused or if that confusion is associated with other concerning signs, such as chest pain, shortness of breath, or elevated blood pressure, they should go to the emergency department.
Dr. McAlpine is an assistant professor in the division of neurological infections and global neurology at Yale School of Medicine.
