Chronic fatigue syndrome (CFS) is characterized by prolonged, debilitating fatigue that does not improve with rest and may be worsened by physical and mental activity. This fatigue must be present for at least 6 months. This syndrome affects more than 1 million individuals in the U.S. and shares symptoms with many medical and psychiatric illnesses, particularly depression.
Keeping in mind that a patient who presents with fatigue could have depression and CFS, follow DSM-IV-TR criteria for major depressive disorder to help identify clinical factors that distinguish the 2 disorders.1
1 Depressed mood
Individuals with major depressive disorder report being depressed most of time and often cannot provide a reason or identify a loss to explain their depressed mood. CFS patients are more likely to report feeling discouraged and depressed because a lack of energy leaves them unable to complete tasks.
2 Diminished interest in activities
Depressed patients typically report a loss or lack of interest in pleasurable activities. CFS patients say they would engage in favorite activities more if their energy level would allow it.2
3 Weight loss and decreased appetite
A depressed patient may report no interest in food or may overeat. CFS patients are interested in food but find shopping and meal preparation fatiguing. Their nutritional intake may consist of fast food or easily prepared meals.
Depressed patients will report poor sleep or excessive sleep (insomnia or hypersomnia). CFS patients experience unrefreshing sleep regardless of how long they sleep.
5 Fatigue or loss of energy
Patients with major depressive disorder will report fatigue regardless of the task. They often view all tasks as equally difficult. CFS patients present with overwhelming fatigue. They express a desire to do more but are physically unable. These patients experience postexertional malaise typically worsening 12 to 48 hours after an activity and lasting for days to weeks.2 Therefore, CFS patients may avoid normal activity.3
6 Feelings of worthlessness or guilt
Guilt in major depressive disorder is often delusional and broad, extending to all areas of life. CFS patients will report guilt caused by their inability to be more active. They may feel they are letting their family or co-workers down. Some people—including some health care providers—do not regard CFS as a “real disease;” others may criticize these patients’ work and daily activity level, therefore increasing guilt.
7 Diminished ability to think or concentrate
In depressed patients, this symptom should improve with antidepressant therapy. In patients with CFS, antidepressants often do not improve concentration or memory.
8 Thoughts of death and suicide
Depressed patients often will have suicidal ideation and believe life is hopeless. CFS patients can become depressed and suicidal because of the condition’s prolonged debilitating symptoms. They may qualify suicidal thoughts with, “If I have to live like this for the rest of my life, I’d rather be dead.”
9 Medical complaints
Depressed and CFS patients often present with medical complaints and require a medical workup. Chronic symptoms— such as muscle pain, headache, multijoint pain without swelling or redness, sore throat, and tender lymph nodes—constitute some of the core symptom criteria of CFS.3 These symptoms may overlap with depressed patients’ somatic complaints.
History of symptom onset and complete medical workups are important to make an accurate diagnosis. Rule out other medical disorders such as fibromyalgia, chronic mononucleosis, hypothyroidism, and subacute infections in patients who present with prolonged fatigue.