Causes

Causes

Theories abound about the causes of chronic fatigue syndrome. Indeed, no primary cause has been found that explains all cases of CFS, and no consistent biologic factors allow objective measures, such as blood tests or brain scans, to definitively diagnose the condition.

Overall, however, doctors are increasingly adopting the view that CFS probably denotes a disease category that includes a range of subtypes, in the same way that cancer is a broad term within which numerous specific forms occur. Mounting evidence suggests that different subtypes of CFS have different causes and manifestations, and that these various types require different treatment approaches.

Research on subgroups of CFS is underway, but is still in very early stages. To date, however, clinical experience and limited data suggest that subgroups of CFS may include the following:

• Post-ADD CFS: Young adults who had attention-deficit disorder as children, who have flipped from hyperactivity to fatigue. Such patients have severe hypersomnolence (sleeping too much, sleeping any time or anywhere). Such patients respond well to psychostimulants.
• Neurological CFS: Patients have more severe cognitive symptoms than patients in the other groups, including trouble thinking, remembering, and paying attention. While cognitive difficulties affect the vast majority of patients with CFS, this group experiences significantly more severe symptoms. Visual-spatial problems are common as are sensitivities to light and noise. Other symptoms in this group include seizure-like episodes and other abnormalities suggestive of temporal lobe seizures. Patients in this group tend to have severe sleep problems in which they never achieve stages 3 or 4 of the sleep cycle, awaken unrefreshed, and respond well to sleep-improving drugs.
• Post-viral CFS versus gradual-onset CFS: According to some experts, an estimated 70% of patients are healthy until a particular illness strikes at a definite time. In gradual-onset patients, however, symptoms develop gradually, and patients are unable to recall any specific viral or infectious illness that initiated the process.
• Patients with immune abnormalities versus those without such abnormalities: Immune dysfunction (such as CD4, CD8, RNase, and TH1-TH2 imbalances) can leave some CFS patients both unable to fight viruses effectively and launching wrongful attacks against healthy tissues. Other CFS patients, however, do not have these immune abnormalities, or have only borderline shifts in immune factors.
• CFS with Orthostatic Intolerance or Neurally Mediated Hypotension (NMH). These conditions cause dizziness (or unconsciousness) when a person stands up due to a drop in blood pressure.
• CFS with neuroendocrine abnormalities: Such problems may include dysregulation of cortisol or ACTH levels.
• Activity level: There may be a difference between low-active versus high-active patients.
• Patients with CFS alone: This subgroup may be different than CFS in patients with other conditions such as fibromyalgia or multiple chemical sensitivity.