NASA Human Research Program Investigators' Workshop (2012)
4119.pdf
THE IMMUNE SYSTEM AND PSYCHONEUROENDOCRINE SYSTEM UNDER CONDITIONS OF
LONG DURATION MISSIONS
A .P. Salam1,2, M. Orr3
1
Department of Infectious Diseases and Tropical Medicine, North West London NHS trust
(alexsalam@doctors.org.uk), 2 formerly IPEV/ESA, Concordia Station, Dome C, High Antarctic Plateau, 3
Auckland University, New Zealand
Objectives
To develop a putative complex adaptive system model of links between the immune system and
psychoneuroendocrine system. Explore how this model could provide a framework for related behavioural health
and performance research in the context of long duration missions (LDM).
Background/Motivation
There is increasing understanding of the human body as a complex adaptive system, with a range of interactions and
feedback mechanisms between the subsystems. Our understanding of the human immune and psychoneuroendocrine
systems and their interactions is still limited, however there is an emerging recognition of the complex bidirectional
impact of the systems on one another.
Methods
The putative model was developed via a formal literature review and search of grey literature, augmented by
selected domain expert interviews.
Results
There is a relatively well established literature on the impact of stress and a range of mental disorders (including
depression, anxiety and psychosis) on the immune system, particularly around suppression or impairment, of the
immune system. However there is also newly emerging evidence and theories around the impact of immune system
activation on human psychoneurological function; particularly in the area of pro-inflammatory cytokines triggered
by physical illness contributing to the development of depression and anxiety syndromes.
Discussion and implications for theory and practice
As we look to the International Space Station acting as an analogue for future LDM, developing shared conceptual
models of the challenges and opportunities we face should be a core imperative. A model can be useful for
communication, shaping and stimulating thought, highlighting strengths and predicting gaps in our knowledge and
subsequently guiding future research and development of countermeasures. Our nosological classification of Mental
disorders typically operate at the syndromal level with the understanding that multiple different pathophysiological
and bio-psycho-social etiological processes may lead to the same syndrome, but we still have limited current
understanding of what these processes might be. The bidirectional interactions and feedback between the
immunological and psychoneuroendocrine systems remains a significant opportunity gap in our current knowledge
particularly the impact of immune responses and related fight-flight responses on the development of mental
disorder and related performance impairment. Psychoneuroendocrine responses to infection and injury such as
heightened fear and anxiety, withdrawal and irritability make evolutionary sense as evolved and adapted
mechanisms to protect the organism from further attack at times of increased susceptibility. We still have a
relatively limited understanding of how the human body may interpret the impact or sequelae of space radiation or
microgravity, or indeed crowding, leadership issues, interpersonal conflict, as an attack or threat on the system and
trigger an immune or fight-flight or stress response that contributes to the development of mental disorder. These are
the types of questions or gaps that the emergent putative model would predict as potentially important for future
LDM research.