Activation of the innate immune system is commonly accompanied by a set of behavioural, psychological and physiological changes known as ‘sickness behaviour’. In animals, infection-related sickness symptoms are significantly increased by exposure to psychosocial stress, suggesting that psychological and immune stressors may operate through similar pathways to induce sickness. We used a double-blind, randomised, placebo-controlled design to examine the effect of acute psychological stress on immune and subjective mood responses to typhoid vaccination in 59 men. Volunteers were assigned to one of four experimental conditions in which they were either injected with typhoid vaccine or saline placebo, and then either rested or completed two challenging behavioural tasks. Typhoid vaccine induced a significant rise in participants’ serum levels of interleukin-6 (IL-6) and this response was significantly larger in the stress versus rest conditions. Negative mood increased immediately post-tasks, an effect also more pronounced in the vaccine/stress condition. In the vaccine/stress group, participants with larger IL-6 responses had heightened systolic blood pressure responses to tasks and elevated post-stress salivary levels of the noradrenaline metabolite 3-methoxy-phenyl glycol (MHPG) and cortisol. Our findings suggest that, as seen in animals, psychological and immune stressors may act synergistically to promote inflammation and sickness behaviour in humans.

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BackgroundL-ornithine is a non-essential, non-protein amino acid. Although L-ornithine is contained in various foods, the amount is usually small.Recently, studies have shown that orally administered L-ornithine reduced the stress response in animals.From these findings, we speculated that L-ornithine may play a role in the relieve of stress and improve sleep and fatigue symptoms in humans. Through a randomised, double-blind, placebo-controlled clinical study, we asked if L-ornithine could be beneficial to stress and sleep in healthy workers.MethodFifty-two apparently healthy Japanese adults who had previously felt slight stress as well as fatigue were recruited to be study participants and were randomly divided into either the L-ornithine (400 mg/day) or placebo group. They orally consumed the respective test substance every day for 8 weeks. Serum was collected for the assessment of cortisol and dehydroepiandrosterone-sulphate (DHEA-S). Perceived mood and quality of sleep were measured by the Profile of Mood States (POMS), Athens Insomnia Scale (AIS), and Ogri-Shirakawa-Azumi sleep inventory MA version (OSA-MA).ResultsSerum cortisol levels and the cortisol/DHEA-S ratio were significantly decreased in the L-ornithine group in comparison with the placebo group. Also, anger was reduced and perceived sleep quality was improved in the L-ornithine group.ConclusionL-ornithine supplementation has the potential to relieve stress and improve sleep quality related to fatigue, both objectively and subjectively.

This study investigated self-perceived work-related stress, along with salivary IgA (s-IgA), cortisol and 3-methoxy-4-hydroxyphenyl glycol (MHPG) in 38 neonatal intensive care unit (NICU) nurses and 26 general ward (GW) nurses. To adjust for sociodemographic characteristics, the two groups of nurses were strictly matched for age, gender (feminine), average work experience and marital status (unmarried). General fatigue and anxiety were significantly higher, and depressive mood tended to be higher, in NICU nurses compared to GW nurses, based on Cumulative Fatigue Symptoms Index scores (p < 0.05, p < 0.05, p = 0.079, respectively). s-IgA concentrations were also inversely correlated with self-perceived work-related stress and were significantly lower in NICU nurses than in GW nurses (p < 0.01). There tended to be a positive association between high cortisol concentrations and the CFSI subscale of depressive mood in both NICU and GW nurses (p = 0.053). Cortisol and MHPG levels were not different between NICU and GW nurses. These work-related stress markers, both self-perceived (CFSI) and biological (s-IgAand cortisol concentrations), highlight the importance of creating and sustaining healthy work environments for NICU and GW nurses.

In the newborn infant, diurnal increase in cortisol was observed in the late afternoon and in correspondence with the birth time. The adrenal circadian rhythm acquired in utero may be reentrained by endocrinological events at birth. Such complex regulation of the adrenal circadian clock may inhibit a swift synchronization of the circadian clock to the day-night rhythm.