Review highlights:

• We review stress signal sensitivity of immune cells in chronic stress and fatigue.
• Chronic stress seems to result in resistance of immune cells to stress signals.
• Findings on stress signal sensitivity under acute stress were inconclusive.
• Pathological consequences (self-maintaining inflammation, fatigue) are discussed.

Review abstract:

Chronic stress and its subsequent effects on biological stress systems have long been recognized as predisposing and perpetuating factors in chronic fatigue, although the exact mechanisms are far from being completely understood.

In this review, we propose that sensitivity of immune cells to glucocorticoids (GCs) and catecholamines (CATs) may be the missing link in elucidating how stress turns into chronic fatigue.

We searched for in vitro studies investigating the impact of GCs or CATs on mitogen-stimulated immune cells in chronically stressed or fatigued populations, with 34 original studies fulfilling our inclusion criteria. Besides mixed cross-sectional findings for stress- and fatigue-related changes of GC sensitivity under basal conditions or acute stress, longitudinal studies indicate a decrease with ongoing stress.

Research on CATs is still scarce, but initial findings point towards a reduction of CAT sensitivity under chronic stress. In the long run, resistance of immune cells to stress signals under conditions of chronic stress might translate into self-maintaining inflammation and inflammatory disinhibition under acute stress, which in turn lead to fatigue.

Dysregulated stress signal sensitivity and inflammatory disinhibition as a pathophysiological mechanism of stress-related chronic fatigue, by Jana Strahler, Nadine Skoluda, Nicolas Rohleder, Urs M Nater in Neuroscience and Biobehavioural Reviews, Vol 68, September 2016, pp 298–31818 [Published online May 2016]