Exploding the myth of depression

The hypothesis that depression is at the root of the symptoms of ME/CFS – a myth particularly prevalent in the 1990s – is slowly crumbling. In fact, a review in 2008 described the range of symptoms that the two illnesses do not share, and listed biological abnormalities separating ME/CFS from depression, such as sleep problems (reduced REM sleep latency in depression but reduced slow-wave deep sleep in ME/CFS) and hypothalamus and pituitary function (circulating cortisol levels are high in depression but low in ME/CFS, compared with controls).

Further evidence of differences has come in a report from Harvard Medical School which compared electroencephalogram (EEG) data from the brains of different groups of patients. The researchers employed “spectral coherence”, a complex computational derivative of EEG spectral data, which estimates connectivity between brain regions.

Their study involved 390 healthy volunteers, 70 people with ME/CFS, 24 people meeting DSM-IV criteria for major depression, and 148 people with unspecified fatigue. Using “principal components analysis” on the EEG results, the team was able to identify and classify correctly approximately 90% of the 47 unmedicated ME/CFS patients and 82 to 92% of the healthy controls. Importantly, no person with depression was classified as having ME/ CFS. The researchers say that this fundamental finding indicates that ME/CFS patients “manifest patterns of functional brain coupling that differ from those of normal controls”, something that “may help explain known differences in cognition, memory, sleep” that afflict patients.

Furthermore, their finding of bilateral temporal lobe involvement in 9 out of 10 of the most discriminating coherence factors could be clinically highly significant since greater temporal lobe involvement is consistent with the impairment of global memory that is frequently observed in people with ME/CFS.

Reference: EEG spectral coherence data distinguish chronic fatigue syndrome patients from healthy controls and depressed patients–a case control study. Duffy FH et al. BMC Neurol 2011 Jul 1; 11: 82.

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