Defining Early Life Stress as a Precursor for Autoimmune Disease

The link between traumatic stress and autoimmune rheumatic diseases: A systematic scoping review

BACKGROUND

The impact of traumatic stress on autoimmune rheumatic diseases (ARDs) has been largely overlooked in existing research. This scoping review aimed to systematically examine the research literature relating to the relationship between traumatic stress and ARDs, by identifying study designs, methodologies, and gaps in the current research landscape.

METHODS

The following databases and search interfaces were searched on 15th December 2023: Embase (via Embase.com), Medline (via PubMed), and Web of Science. Additional references were identified via bibliographies of included studies. The following studies were included, with no publication date limit and language restricted to English: targeting the association between traumatic stress and ARDs, observational methodologies, including cohort, case-control, and cross-sectional studies, exclusively focusing on self-reported psychological trauma impacts, such as adverse childhood experiences (ACEs), Post-traumatic Stress Disorder (PTSD), or major life stressors. Two authors independently assessed the studies for inclusion criteria and extracted the data.

RESULTS

This scoping review revealed connections between traumatic stress and ARDs through an analysis of 21 included studies, highlighting the scarcity of research in this area. The studies, primarily from high-income countries and especially the USA, span from 2000 to 2023, indicating a growing interest in recent years and employing a range of methodologies. Traumas such as ACEs, PTSD, and major life events were frequently examined, showing a strong association with an increased risk and severity of ARDs, particularly rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE).

CONCLUSION

This scoping review reveals a notable dearth in research on the impact of traumatic stress, such as ACEs, PTSD, and major life events, on ARDs, especially on rare diseases, yet underscores a significant association between trauma and ARD severity or incidence. It highlights the critical need for future investigations to broaden the scope of ARDs studied, extend research to less represented regions, and utilize diverse, standardized methodologies to deepen our understanding of the trauma-ARD association.

Stress hormones mediate developmental plasticity in vertebrates with complex life cycles

The environment experienced by developing organisms can shape the timing and character of developmental processes, generating different phenotypes from the same genotype, each with different probabilities of survival and performance as adults. Chordates have two basic modes of development, indirect and direct. Species with indirect development, which includes most fishes and amphibians, have a complex life cycle with a free-swimming larva that is typically a growth stage, followed by a metamorphosis into the adult form. Species with direct development, which is an evolutionarily derived developmental mode, develop directly from embryo to the juvenile without an intervening larval stage. Among the best studied species with complex life cycles are the amphibians, especially the anurans (frogs and toads). Amphibian tadpoles are exposed to diverse biotic and abiotic factors in their developmental habitat. They have extensive capacity for developmental plasticity, which can lead to the expression of different, adaptive morphologies as tadpoles (polyphenism), variation in the timing of and size at metamorphosis, and carry-over effects on the phenotype of the juvenile/adult. The neuroendocrine stress axis plays a pivotal role in mediating environmental effects on amphibian development. Before initiating metamorphosis, if tadpoles are exposed to predators they upregulate production of the stress hormone corticosterone (CORT), which acts directly on the tail to cause it to grow, thereby increasing escape performance. When tadpoles reach a minimum body size to initiate metamorphosis they can vary the timing of transformation in relation to growth opportunity or mortality risk in the larval habitat. They do this by modulating the production of thyroid hormone (TH), the primary inducer of metamorphosis, and CORT, which synergizes with TH to promote tissue transformation. Hypophysiotropic neurons that release the stress neurohormone corticotropin-releasing factor (CRF) are activated in response to environmental stress (e.g., pond drying, food restriction, etc.), and CRF accelerates metamorphosis by directly inducing secretion of pituitary thyrotropin and corticotropin, thereby increasing secretion of TH and CORT. Although activation of the neuroendocrine stress axis promotes immediate survival in a deteriorating larval habitat, costs may be incurred such as reduced tadpole growth and size at metamorphosis. Small size at transformation can impair performance of the adult, reducing probability of survival in the terrestrial habitat, or fecundity. Furthermore, elevations in CORT in the tadpole caused by environmental stressors cause long term, stable changes in neuroendocrine function, behavior and physiology of the adult, which can affect fitness. Comparative studies show that the roles of stress hormones in developmental plasticity are conserved across vertebrate taxa including humans.