The "you're crazy, it's all in your mind" school of thought on chronic fatigue syndrome (CFS) continues to recede into ancient history. There were those who attributed the brain fog (and all of CFS) to depression — which was, well, crazy.

In one study, 57 women with CFS were evaluated for cognitive function using neuropsychological tests that measure mental acuity in areas such as ability to pay attention, to count forward and backward, auditory-verbal learning skills, executive functions, and psychomotor skills.

Participants were divided into two groups, with one group including those CFS patients who suffered depression (based on clinical assessment to determine scores on the Hospital Anxiety and Depression Scale) and the other including those CFS patients who were not determined to be depressed.

The results showed no difference between the two groups in their levels of cognitive deficit in performing attention and executive functions.

Researchers therefore concluded that there was no link between depression and the cognitive impairments exhibited by patients with CFS