Assessing salivary cortisol in studies of child development

In a series of studies, we evaluated the susceptibility of radioimmunoassay s (RIA) for saliva cortisol to interference effects caused by oral stimulan ts used to facilitate saliva collection in studies with children. When adde d directly to saliva samples, oral stimulants (drink mix crystals) artifici ally inflated estimated cortisol concentrations. The magnitude of the inter ference effect was concentration-dependent and more pronounced for some sti mulants and RTA procedures than for others. Analysis of samples collected u sing oral stimulants from child and adult participants confirmed stimulant interference as an extraneous source of variability in measured saliva cort isol. Associations between serum and saliva cortisol and between saliva cor tisol and "behavioral" variables were attenuated by stimulant interference. A survey of six large child studies estimated interference effects, indexe d by low sample pH, to be present in 14.7% of the 1,148 total saliva sample s, or 2%-54% (M = 22%) of samples within each study. Recommendations to min imize the impact of stimluant interference in studies involving salivary co rtisol in the context of child health and development are outlined.