Depression

Depression or low mood and the more severe major depressive disorder (clinical depression) are common but potentially serious mood disorders. Depression causes severe symptoms that affect how someone feels, thinks, and handles daily activities, such as sleeping, eating, or working. To be diagnosed with depression, the symptoms must be present for at least two weeks.

Depression as expressed in patients with ME/CFS is generally considered as secondary depression or reactive depression due to the debilitating effects of ME/CFS. Secondary or reactive depression is common in many chronic illnesses as well as cancer, which may be an acute or chronic illness.

Misdiagnosis of ME/CFS
ME/CFS is often misdiagnosed as depression, as many symptoms can overlap. Older case definitions, such as the Fukuda criteria and the Holmes criteria do not differentiate enough between the symptomatic criteria of depression and chronic fatigue syndrome (CFS).

Differences between depression and ME/CFS
Hawk, Jason, and Torres-Harding defined a number of key symptoms that were worse or different in ME/CFS compared to clinical depression without ME/CFS:
 * Significant post-exertional malaise (PEM) was found in ME/CFS patients
 * PEM is now a required diagnostic criteria for ME/CFS in most countries

Using the symptoms above list, Hawk, Jason, and Torres-Harding were able to report 100% correct classification between patients with major depressive disorder versus ME/CFS.
 * fatigue lasts for a greater the percentage of the time in ME/CFS
 * unrefreshing sleep severity is higher
 * confusion–disorientation severity is higher
 * shortness of breath severity is higher
 * ME/CFS patients have less self-reproach (as scored on the Beck Depression Inventory)

LaFerney, a psychiatric clinical nurse specialist, adds: Dr. Sarah Myhill adds an additional difference between depression and CFS: Clinical trials and patient evidence have both shown that:
 * Reason for depression: Individuals with major depressive disorder often cannot provide a reason or identify a loss to explain their depressed mood. ME/CFS patients are more likely to report feeling discouraged and depressed because of the inability to perform tasks, be employed, or engage in social functions due to ME/CFS symptoms.
 * No lack of interest in activities: Depressed patients typically report a lack of interest in activities they previously enjoyed. ME/CFS patients say they would engage in favorite activities more if their illness would allow it.
 * Post-exertional malaise: Although both depressed and ME/CFS patients report fatigue, only ME/CFS report post-exertional malaise: with physical symptoms typically worsening 12 to 48 hours after an activity and lasting for days to weeks.
 * Antidepressants don't help in ME/CFS: In depressed patients, the diminished ability to think or concentrate should improve with antidepressant drugs or therapies. In patients with ME/CFS, antidepressants often do not improve concentration or memory.
 * Response to exercise: Exercise makes CFS patients much worse, but can be positively therapeutic in pure depression
 * Cognitive behavioral therapy aimed at ME/CFS symptoms is ineffective and often harmful, and can harm mental health, but is an effective evidence-based treatment for depression
 * most ME/CFS patients do not have depression, although in common with other chronic illness a significant number of patients develop reactive or secondary depression
 * Many physically abnormal findings that are not present in depression, but many of these findings are not from the standard diagnostic tests and no single finding can yet act as a diagnostic biomarker for ME/CFS. Physical abnormalities in ME/CFS indicate immune, neurological, energy transportation, and other findings that cannot be explained by depression, somatization, deconditioning, health anxiety, or other psychological or behavioral factors

If I was cured tomorrow...
The Forgotten Plague Facebook page had a "If I was cured tomorrow..." campaign encouraging ME/CFS patients to upload their dreams to highlight this difference from depression.

Fukuda criteria
In 2006, Hawk, Jason, and Torres-Harding found that the CDC's Fukuda ME/CFS criteria, which is now retired from use, only correctly classified 84.4% of patients when comparing patients with major depressive disorder and to patients with ME/CFS.

Prevalence

 * Katrina Berne reports a prevalence of 65-90% for depression.

Symptom recognition

 * In the 1988 Holmes criteria, depression is an optional criteria for diagnosis, under the section Minor Symptom Criteria - Neuropsychologic Complaints. It is not a diagnosable symptom in the current CDC criteria, the Fukuda criteria, the Canadian Consensus Criteria or the International Consensus Criteria although secondary depression is recognized as a possible symptom and comorbidity of ME/CFS in the International Consensus Criteria.

Notable studies

 * 2006, Differential diagnosis of chronic fatigue syndrome and major depressive disorder (Full Text)
 * 2008, A Systematic Review of Chronic Fatigue Syndrome: Don't Assume It's Depression (Full Text)

Possible causes
Depression in ME/CFS patients may be caused by:
 * The impact of living with a poorly understood chronic illness, known as reactive depression or secondary depression
 * Someone with ME/CFS may have depression unrelated to their ME/CFS symptoms, known as primary depression
 * People with ME/CFS typical lose the natural benefit of exercise, which means a person who previously used exercise to improve their mood is no longer able to do this
 * Depression is a potential side effect of some drugs, particularly a class of drugs known as mood stabilizers, which are used for bipolar depression (manic depression) but cause depression or worsen depression in people without bipolar disorder.

Potential treatments

 * Antidepressants
 * Cognitive behavioral therapy for depression (CBT)
 * Mindfulness and Meditation

Learn more

 * 2008, A Systematic Review of Chronic Fatigue Syndrome: Don’t Assume It’s Depression
 * 2008, Depression or chronic fatigue syndrome? by Michael C. Laferney
 * 2014, How to Prove to Your Doctor You’ve Got Chronic Fatigue Syndrome (ME/CFS) And Are Not Just Depressed by Cort Johnson