Chronic pain constitutes a challenge for the scientific community and a significant economic and social cost for modern societies. Given the failure of current drugs to effectively treat chronic pain, which are based on suppressing aberrant neuronal excitability, we propose in this review an integrated approach that views pain not solely originating from neuronal activation but also the result of a complex interaction between the nervous, immune, and endocrine systems. Pain assessment must also extend beyond measures of behavioural responses to noxious stimuli to a more developmentally informed assessment given the significant plasticity of the nociceptive system during the neonatal period. Finally integrating the concept of perinatal programming into the pain management field is a necessary step to develop and target interventions to reduce the suffering associated with chronic pain. We present clinical and animal findings from our laboratory (and others) demonstrating the importance of the microbial and relational environment in programming pain responsiveness later in life via action on hypothalamo-pituitary adrenal (HPA) axis activity, peripheral and central immune system, spinal and supraspinal mechanisms, and the autonomic nervous system.

There is considerable evidence that early life stress (ELS) can have a lasting impact upon adult physiology. Various childhood (and even prenatal) stressors such as parental separation, neglect, and trauma, can leave an enduring impact upon immune, autonomic and endocrine systems. These changes are increasingly understood to represent vulnerabilities to developing later life medical (and psychological) morbidity. In this article it is hypothesized that these enduring physiological changes may also serve as markers to detect the presence of ELS or rather it's impact upon the individual. Until now, the detection of ELS has relied primarily upon self-report measures that have obvious limitations. If a reliable and objective means of detecting the impact of ELS can be established using physiological means, then one potential application would be in the chronic pain population. At present it remains unclear why for a given injury, some acute pain subjects progress to develop chronic pain, while others make a full recovery. The evidence to date points more to psychosocial factors than nociceptive parameters. The hypothesis proposed in this manuscript that ELS results in altered physiological reactivity may offer in part an explanation for this puzzling variable transition to chronic pain.

There is a rapidly accumulating body of evidence regarding the influential role of early life stress (ELS) upon medical and psychiatric conditions. While self-report instruments, with their intrinsic limitations of recall, remain the primary means of detecting ELS in humans, biological measures are generally limited to a single biological system. This paper describes the design, rationale and feasibility of a study to simultaneously measure neuroendocrine, immune and autonomic nervous system (ANS) responses to psychological and physiological stressors in relation to ELS. Five healthy university students were recruited by advertisement. Exclusion criteria included chronic medical conditions, psychotic disorders, needle phobia, inability to tolerate pain, and those using anti-inflammatory medications. They were clinically interviewed and physiological recordings made over a two-hour period pre, during and post two acute stressors: the cold pressor test and recalling a distressing memory. The Childhood Trauma Questionnaire and the Parental Bonding Index were utilised to measure ELS. Other psychological measures of mood and personality were also administered. Measurements of heart rate, blood pressure, respiratory rate, skin conductance, skin blood flow and temporal plasma samples were successfully obtained before, during and after acute stress. Participants reported the extensive psychological and multisystem physiological data collection and stress provocations were tolerable. Most (4/5) participants indicated a willingness to return to repeat the protocol, indicating acceptability. Our protocol is viable and safe in young physically healthy adults and allows us to assess simultaneously neuroendocrine, immune and autonomic nervous system responses to stressors in persons assessed for ELS.

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