The cortisol awakening response (CAR), the marked increase in cortisol secretion over the first 30-45 min after morning awakening, has been related to a wide range of psychosocial, physical and mental health parameters, making it a key variable for psychoneuroendocrinological research. The CAR is typically assessed from self-collection of saliva samples within the domestic setting. While this confers ecological validity, it lacks direct researcher oversight which can be problematic as the validity of CAR measurement critically relies on participants closely following a timed sampling schedule, beginning with the moment of awakening. Researchers assessing the CAR thus need to take important steps to maximize and monitor saliva sampling accuracy as well as consider a range of other relevant methodological factors. To promote best practice of future research in this field, the International Society of Psychoneuroendocrinology initiated an expert panel charged with (i) summarizing relevant evidence and collective experience on methodological factors affecting CAR assessment and (ii) formulating clear consensus guidelines for future research. The present report summarizes the results of this undertaking. Consensus guidelines are presented on central aspects of CAR assessment, including objective control of sampling accuracy/adherence, participant instructions, covariate accounting, sampling protocols, quantification strategies as well as reporting and interpreting of CAR data. Meeting these methodological standards in future research will create more powerful research designs, thus yielding more reliable and reproducible results and helping to further advance understanding in this evolving field of research.

Empirical evidence suggests that there are marked associations between positive psychological states and health outcomes, including reduced cardiovascular disease risk and increased resistance to infection. These observations have stimulated the investigation of behavioral and biological processes that might mediate protective effects. Evidence linking positive affect with health behaviors has been mixed, though recent cross-cultural research has documented associations with exercising regularly, not smoking, and prudent diet. At the biological level, cortisol output has been consistently shown to be lower among individuals reporting positive affect, and favorable associations with heart rate, blood pressure, and inflammatory markers such as interleukin-6 have also been described. Importantly, these relationships are independent of negative affect and depressed mood, suggesting that positive affect may have distinctive biological correlates that can benefit health. At the same time, positive affect is associated with protective psychosocial factors such as greater social connectedness, perceived social support, optimism, and preference for adaptive coping responses. Positive affect may be part of a broader profile of psychosocial resilience that reduces risk of adverse physical health outcomes.

Researchers interested in the neurobiology of the acute stress response in humans require a valid and reliable acute stressor that can be used under experimental conditions. The Trier Social Stress Test (TSST) provides such a testing platform. It induces stress by requiring participants to make an interview-style presentation, followed by a surprise mental arithmetic test, in front of an interview panel who do not provide feedback or encouragement. In this review, we outline the methodology of the TSST, and discuss key findings under conditions of health and stress-related disorder. The TSST has unveiled differences in males and females, as well as different age groups, in their neurobiological response to acute stress. The TSST has also deepened our understanding of how genotype may moderate the cognitive neurobiology of acute stress, and exciting new inroads have been made in understanding epigenetic contributions to the biological regulation of the acute stress response using the TSST. A number of innovative adaptations have been developed which allow for the TSST to be used in group settings, with children, in combination with brain imaging, and with virtual committees. Future applications may incorporate the emerging links between the gut microbiome and the stress response. Future research should also maximise use of behavioural data generated by the TSST. Alternative acute stress paradigms may have utility over the TSST in certain situations, such as those that require repeat testing. Nonetheless, we expect that the TSST remains the gold standard for examining the cognitive neurobiology of acute stress in humans.

Positive affect has been associated with favourable health outcomes, and it is likely that several biological processes mediate the effects of positive mood on physical health. There is converging evidence that positive affect activates the neuroendocrine, autonomic and immune systems in distinct and functionally meaningful ways. Cortisol, both total output and the awakening response, has consistently been shown to be lower among individuals with higher levels of positive affect. The beneficial effects of positive mood on cardiovascular function, including heart rate and blood pressure, and the immune system have also been described. The influence of positive affect on these psychobiological processes are independent of negative affect, suggesting that positive affect may have characteristic biological correlates. The duration and conceptualisation of positive affect may be important considerations in understanding how different biological systems are activated in association with positive affect. The association of positive affect and psychobiological processes has been established, and these biological correlates may be partly responsible for the protective effects of positive affect on health outcomes.

The relationship between morningness/eveningness (M/E) and morning-to-afternoon cortisol ratio, pubertal timing, and antisocial behavior was examined in 111 girls and boys ages 8 to 13 years. Cortisol levels showed a significant increase after awakening and declined thereafter (p<.05). Eveningness was related to a composite measure of antisocial behavior and rule-breaking and attention behavior problems and conduct disorder (CD) symptoms in boys and relational aggression in girls. In boys only, lower a.m. to p.m. cortisol ratio, indicating less circadian decrease in cortisol, was related to attention problems. Early pubertal timing was associated with boys' rule-breaking and attention behavior problems and CD symptoms and girls' relational aggression. The findings indicate that evening activity preference; extreme a.m. to p.m. cortisol ratios, in one case; and early pubertal timing were associated with antisocial behavior even in young adolescents, but the findings were stronger for boys than for girls.