Cumulative stress pathophysiology in schizophrenia as indexed by allostatic load

Abstract

Background The etiopathophysiology of schizophrenia has long been linked to stress and the influence of stress is important in all stages of the illness. Previous examinations of perceived stress and acute stress responses may not capture this longitudinal stress pathophysiology. We hypothesized that the cumulative negative effects of stress, indexed by allostatic load (AL), would be elevated in schizophrenia, and that the AL paradigm would be relevant to our understanding of pathophysiology in schizophrenia. Methods We assessed allostatic load in 30 patients with schizophrenia (SZ; mean age=33; 17 males) and 20 healthy controls (HC; mean age=35; 12 males) using 13cardiovascular, metabolic, neuroendocrine and immune biomarkers. Participants’ perceived stress over the past month; functional capacity and psychiatric symptoms were also measured. Results Controlling for age, SZ had significantly higher AL as compared to HC (p=0.007). Greater AL was present in both early course and chronic SZ, and was associated with reduced functional capacity (p=0.006) and more psychotic symptoms (p=0.048) in SZ. Current level of perceived stress was not significantly elevated in SZ or associated with AL in either group. Conclusions The higher AL found in SZ may reflect increased bodily “wear and tear”, possibly caused by more chronic stress exposure or maladaptive responses to stress over time, although additional research is required to differentiate these causes. The higher AL is similarly present in early and chronic SZ, suggesting primary maladaptive stress physiology rather than secondary effects from medications or chronic illness.

Allostatic load in early pregnancy is associated with poor sleep quality

“…The allostatic load concept models allostatic load as a measure of cumulative physiologic wear and tear. Although few studies have explored the relationship between subjective measures of acute stress and allostatic load, the lack of a strong correlation between measures of acute stress and AL is unsurprising and consistent with the conceptual model [1, 3, 36]. Thus, the AL model is positively correlated with chronic stressors, such as low socioeconomic status or poor sleep quality, but not acute stressors.…”

Abnormal glycemic homeostasis at the onset of serious mental illnesses: A common pathway

“…AL relates to the situation where under repeated or chronic stress, the physiological homeostasis systems through the entire body become unbalanced and prone to developing diverse diseases. The concept of AL has been examined in bipolar disorder (Grande et al, 2012), major depressive disorder (Wilkinson and Goodyer, 2011) and schizophrenia (Nugent et al, 2015). …”

Allostatic load and reduced cortical thickness in schizophrenia

“…Allostatic load index provides a means to account for the systemic pathophysiological effects of cumulative stress exposure in psychiatric disorders. Previously, we found higher levels of allostatic load in patients with schizophrenia; and allostatic load was associated with worse functional capacity (Nugent et al, 2015). How elevated allostatic load may impact the brains of schizophrenia patients is unknown and is the focus on this study.…”

“…Blood pressure and heart rate was measured after at least 10 minutes of rest. Allostatic load data for 26 patients and 17 controls in this study were reported in a previous publication (Nugent et al, 2015). …”