Neurasthenia and Burnout | Is 'Nervous Exhaustion' a 19th-Century Term for HPA Axis Dysregulation?

Neurasthenia, a term coined in the late 19th century by American neurologist George Miller Beard, translates to "nervous exhaustion." It was diagnosed based on symptoms of fatigue, anxiety, headaches, irritability, and a general feeling of being unable to cope with the stresses of modern life. The prevailing theory at the time was that the pressures of industrialization, intellectual work, and urban living were depleting a finite resource of "nervous energy" stored in the central nervous system. This depletion was thought to be the direct cause of the wide-ranging physical and mental symptoms. While the concept of "nervous energy" is now obsolete, the description of a state of profound exhaustion resulting from chronic stress resonates with modern concepts. It was considered a physical illness of the nerves, not a psychological failing, and its diagnosis was widespread among the educated classes in North America and Europe, reflecting a societal concern with the rapid pace of change and its impact on human physiology.

The Hypothalamic-Pituitary-Adrenal (HPA) axis is the body's primary stress response system. When faced with a stressor, the hypothalamus releases a hormone that signals the pituitary gland, which in turn signals the adrenal glands to release cortisol. Cortisol is the main stress hormone, preparing the body for "fight or flight." HPA axis dysregulation occurs when this system is chronically activated by prolonged stress. Instead of a healthy, fluctuating rhythm, cortisol levels can become chronically elevated or, conversely, blunted and flattened. This disrupts sleep, metabolism, immune function, and mood. 'Burnout' is the experiential outcome of this physiological state. It is characterized by three main dimensions: overwhelming exhaustion, feelings of cynicism and detachment from one's job or life, and a sense of ineffectiveness. It is not simply feeling tired; it is a state of profound depletion caused by a mismatch between the demands placed upon an individual and their available resources, a process directly underpinned by the malfunctioning of the HPA axis.

The overlap in symptoms between neurasthenia and burnout is significant. The defining feature of both is debilitating fatigue that is not alleviated by rest. Other shared symptoms include cognitive difficulties often described as "brain fog," increased irritability, anxiety, depressed mood, and various physical complaints like headaches and muscle pain (somatic symptoms). While neurasthenia was a broad diagnostic category and burnout is often tied specifically to occupational stress, both describe a state of energetic depletion. This suggests they are different historical and cultural labels for a very similar human experience of being overwhelmed by chronic, inescapable stress to the point of physiological and psychological collapse.

The biological link is HPA axis dysregulation. The 19th-century concept of depleted "nervous energy" can be understood as a prescient, albeit imprecise, description of the neuroendocrine consequences of chronic stress. Persistent activation of the HPA axis leads to changes in brain structure and function, particularly in the prefrontal cortex, hippocampus, and amygdala—areas crucial for executive function, memory, and emotional regulation. The resulting hormonal imbalance, especially of cortisol, directly affects neurotransmitter systems (like serotonin and dopamine) and cellular energy processes. This provides a clear biological basis for the symptoms of fatigue, mood disturbance, and cognitive impairment seen in both neurasthenia and burnout.

Neurasthenia faded from Western medical vocabulary, particularly in the American DSM (Diagnostic and Statistical Manual of Mental Disorders), by the mid-20th century. It was criticized for being too vague and encompassing a wide array of symptoms that could belong to other conditions. As psychiatry evolved, its symptoms were absorbed into more specific diagnoses, primarily anxiety and depressive disorders. However, this reclassification may have lost a key element: the explicit link between the symptoms and a state of chronic exhaustion from life's demands, rather than an internal chemical imbalance alone. Interestingly, the concept persists in other diagnostic systems, such as the ICD (International Classification of Diseases) and in Chinese medicine (*Shenjing Shuairuo*), indicating its continued clinical utility. The recent rise of 'burnout' as a widely accepted concept suggests a renewed need for a term that specifically describes exhaustion syndromes caused by chronic stress, filling the void left by neurasthenia.