Chronic fatigue syndrome (CFS) is characterized by fatigue, sleep dysfunction, and cognitive deficits (Fukuda et al., 1994). Research surrounding cognitive functioning among patients with CFS has found difficulty with memory, attention, and information processing. A similar disorder, postural tachycardia syndrome (POTS), is characterized by increased heart rate, fatigue, and mental cloudiness (Raj et al., 2009). Potential implications of cognitive deficits for patients with CFS and/or POTS are discussed, including difficulties with school and/or employment. A few biological theories (i.e., kindling, impairments in the central nervous system, and difficulty with blood flow) have emerged as potential explanations for the cognitive deficits reported in both CFS and POTS Future research should continue to examine possible explanations for cognitive impairments in CFS and POTS, and ultimately use this information to try and reduce cognitive impairments for these patients.

Individuals with orthostatic intolerance (OI) often experience ill‐defined neurocognitive impairment, typically referred to by patients as brain fog. The objective of this study was to evaluate brain fog to further insight on its mechanism and potential treatments. Eligible subjects, 14–29 yrs diagnosed with OI, were recruited through ads on online support groups. Participants electronically completed a 38‐item questionnaire designed for this study. Of 116 participants (91% F), 111 reported brain fog. The symptoms most concurrent with brain fog were fatigue (88%), lightheadedness (78%), headaches (75%), and palpitations (68%). The most frequent triggers were fatigue (95%), lack of sleep (94%), prolonged standing (93%), and heat (85%). The best preventive strategies were staying cool (69%), high fluid intake (65%), high salt intake (62%), and compression stockings (44%). The interventions most frequently reported to improve brain fog were intravenous saline (74%), stimulants (64%), salt tablets (52%), IM vitamin B12 (52%), and midodrine (44%). Brain fog is associated with the onset of typical OI symptoms and triggers that exacerbate OI. Yet, some endorsed treatments are not commonly used to treat OI and deserve further study in this population.