Impairments in cognitive performance in chronic fatigue syndrome are common, not related to co-morbid depression but do associate with autonomic dysfunction, by
Lucy J Robinson, Peter Gallagher, Stuart Watson, Ruth Pearce, Andreas Finkelmeyer, Laura Maclachlan, Julia L Newton in  PLoS ONE 14 (2) [Published: February 5, 2019]

Research abstract:

Objectives:
To explore cognitive performance in chronic fatigue syndrome (CFS) examining two cohorts. To establish findings associated with CFS and those related to co-morbid depression or autonomic dysfunction.

Methods:
Identification and recruitment of participants was identical in both phases, all CFS patients fulfilled Fukuda criteria. In Phase 1 (n=48) we explored cognitive function in a heterogeneous cohort of CFS patients, investigating links with depressive symptoms (HADS). In phase 2 (n=51 CFS & n=20 controls) participants with co-morbid major depression were excluded (SCID). Furthermore, we investigated relationships between
cognitive performance and heart rate variability (HRV).

Results:
Cognitive performance in unselected CFS patients is in average range on most measures. However, 0-23% of the CFS sample fell below the 5thpercentile. Negative correlations occurred between depressive symptoms (HAD-S) with Digit-Symbol-Coding (r=-.507, p=.006) and TMT-A (r=-.382, p=.049). In CFS without depression, impairments of cognitive performance remained with significant differences in indices of psychomotor speed (TMT-A: p=0.027; digit-symbol substitution: p=0.004; digit-symbol copy: p=0.007; scanning: p=.034) Stroop test suggested differences due to processing speed rather than inhibition.

Both cohorts confirmed relationships between cognitive performance and HRV (digit-symbol copy (r=.330, p=.018), digit-symbol substitution (r=.313, p=.025), colour-naming trials Stroop task (r=.279, p=.050).

Conclusion:
Cognitive difficulties in CFS may not be as broad as suggested and may be restricted to slowing in basic processing speed. While depressive symptoms can be associated with impairments, co-morbidity with major depression is not itself responsible for reductions in cognitive performance. Impaired autonomic control of heart-rate associates with
reductions in basic processing speed.

Graphic from pngtree.com
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