Cognitive dysfunction is a common and disabling clinical feature of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), often described by patients as “brain fog.” These symptoms typically manifest as difficulties in attention, memory, and concentration. Chronic stress has been proposed as an important contributing factor in ME/CFS. The hypothalamic-pituitary-adrenal (HPA) axis plays a central role in the stress response, and prolonged adverse stress may contribute to HPA axis dysregulation, including altered cortisol rhythmicity and impaired negative feedback regulation. Such dysregulation may be associated with cognitive dysfunction in ME/CFS through mechanisms involving neuroinflammatory responses, oxidative stress, and disturbances in neurotransmitter homeostasis. Studies suggest that these alterations may affect hippocampal structure and function, thereby contributing to impaired learning and memory processes. As a key brain region involved in cognition and stress regulation, the hippocampus may be implicated in the neurobiological mechanisms underlying cognitive dysfunction in ME/CFS. This review integrates current evidence on the potential role of HPA axis dysregulation and related neurobiological alterations in chronic stress-associated cognitive dysfunction in ME/CFS, with the aim of providing a theoretical basis for identifying potential intervention targets and informing strategies centered on HPA axis regulation.
Kang et al. (2026) studied this question.