“…With regard to the regulation of this system, the activity of the HPA axis has differed in study populations with ASD depending on factors such as individual patterns of sensory sensitivity or stress levels, specific stress paradigm, or type of parameter assessed (saliva or plasma) (Brosnan et al, 2009;Corbett et al, 2006Corbett et al, , 2008Corbett et al, , 2009Hamza et al, 2010;Jansen et al, 2006;Zinke et al, 2010). In typically developing individuals, cortisol levels fluctuate with a diurnal rhythm; these levels begin to increase before awakening, show a rapid rise from awakening over the next 30-45 min, and then fall throughout the day, reaching a low point during the normal sleep cycle, to rise again in preparation for awakening (Clow et al, 2010).…”