Neurasthenia's Legacy | Are CFS and ME the Modern Form of an Old Illness?

Neurasthenia was a medical diagnosis that gained prominence in the late 19th and early 20th centuries. The term, meaning "nerve weakness," was used to describe a collection of symptoms including chronic fatigue, body aches, anxiety, headaches, and irritability. At the time, it was believed to be caused by the exhaustion of the central nervous system's energy reserves, a direct result of the fast pace and increased pressures of modern urban and industrial life. This condition was not strictly classified as physical or mental; instead, it occupied a space in between, seen as a physical manifestation of nervous exhaustion. The diagnosis was applied broadly to a wide range of symptoms that lacked a clear organic cause, making it a common but vaguely defined condition. Physicians like George Miller Beard, who popularized the term, considered it a legitimate physical ailment, though its treatment often involved rest cures, dietary changes, and sometimes ineffective electrical stimulation, reflecting the limited medical understanding of the era. As the fields of psychiatry and neurology advanced, the broad and imprecise nature of neurasthenia led to its gradual replacement by more specific diagnoses.

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a severe, long-term, and multi-system biological illness. Its defining characteristic is post-exertional malaise (PEM), a significant worsening of symptoms after even minimal physical or mental exertion. Other core symptoms include profound and persistent fatigue that is not relieved by rest, unrefreshing sleep, cognitive difficulties often termed "brain fog," and widespread muscle or joint pain. Unlike the historical concept of neurasthenia, ME/CFS is understood today as a distinct pathophysiological disease. Current research points towards a combination of factors, including immune system dysregulation, autonomic nervous system dysfunction, and impaired cellular energy metabolism. It is not a psychological condition, although it can have significant psychological consequences due to its debilitating nature. The onset of ME/CFS often follows an acute viral infection, suggesting a potential trigger that initiates a chronic state of neuro-immune disruption. The diagnosis is made based on specific clinical criteria after ruling out other medical conditions.

The comparison between neurasthenia and ME/CFS arises from their significant symptomatic overlap. Both conditions are primarily characterized by severe fatigue that disrupts daily life. Patients in both eras reported similar complaints of exhaustion, pain, cognitive issues, and a general sense of malaise. This symptomatic similarity is the main reason why some researchers view ME/CFS as the modern manifestation of the patient group previously diagnosed with neurasthenia. In both cases, the conditions were often linked to preceding stressors, whether the "stress of modern life" for neurasthenia or viral infections for ME/CFS. The historical trajectory shows that while the label "neurasthenia" faded in Western medicine, the constellation of symptoms persisted, eventually re-emerging under new diagnostic labels.

The fundamental difference lies in the underlying explanatory model. Neurasthenia was conceptualized through a lens of "nerve weakness," a functional deficit of the nervous system often with psychosomatic or moral overtones. Its treatments were non-specific and aimed at restoring supposed "nervous energy." In stark contrast, the modern medical approach to ME/CFS is grounded in biomedical research. It is investigated as a complex organic disease involving measurable biological abnormalities. Research now focuses on identifying biomarkers, understanding immune and mitochondrial dysfunction, and exploring the neurological basis for symptoms like PEM and brain fog. This represents a critical shift from a psychological or functional framework to a pathophysiological one, treating the illness as a biological reality rather than a problem of disposition or mental fortitude.

The diagnosis of neurasthenia declined in the early to mid-20th century, particularly in North America and Europe, for several reasons. A primary factor was the rise of psychoanalysis and Freudian theory, which reinterpreted many of neurasthenia's symptoms through a purely psychological lens, attributing them to unresolved internal conflicts or anxiety. Concurrently, the field of medicine was advancing towards diagnoses based on specific, observable pathology. Neurasthenia, being a broad syndrome without a clear biological marker, did not fit this new, more stringent biomedical model. Its symptoms were parsed out and re-categorized into more specific psychiatric conditions like anxiety disorders, depressive disorders, and somatoform disorders. As a result, the term was removed from major diagnostic manuals such as the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM). The label became seen as unscientific and obsolete, a relic of a bygone era of medical understanding, even though the patient population experiencing these symptoms continued to exist.