“…There is some evidence that, in adults, higher levels of extraversion and greater positive affect (assessed by trait questionnaire or by averaging self-reported states of positive affect over repeated measurements) associate with a steeper diurnal slope, smaller awakening response, lower total cortisol output, and lower cortisol levels obtained from single measurements taken at varying times during the day (Brummett et al, 2009; Hoyt et al, 2015; Lai et al, 2005; Mikolajczak et al, 2010; Nater et al, 2010; Polk et al, 2005; Steptoe et al, 2007; Steptoe et al, 2008; Steptoe and Wardle, 2005; Steptoe et al, 2005; Turner-Cobb et al, 2008; Vedhara et al, 2006). And conversely, some studies have shown higher levels of neuroticism or trait negative affect related to a flatter diurnal slope, larger morning awakening response, higher total output, and higher cortisol levels on single measurements (Doane et al, 2011; Garcia-Banda et al, 2014; Hauner et al, 2008; Mikolajczak et al, 2010; Nater et al, 2010; Oishi et al, 2012; Polk et al, 2005; Portella et al, 2005). Yet in other studies, similarly assessed personality dimensions and trait affect do not correlate with the same indices of HPA activity (Brummett et al, 2009; Dettling et al, 1999; Ellenbogen et al, 2006; Garcia-Banda et al, 2014; Gerritsen et al, 2009; Hauner et al, 2008; Hoyt et al, 2015; Munafo et al, 2006; Schommer et al, 1999; Steptoe et al, 2008; Turner-Cobb et al, 2008; van Eck et al, 1996; Vedhara et al, 2006; Laceulle et al, 2015) or do so in an opposite direction (Ellenbogen et al, 2006; Hauner et al, 2008; Polk et al, 2005; van Santen et al, 2011, Atkinson et al, 2015).…”