The cortisol awakening response (CAR) can be assessed from saliva samples collected at home, which
confers ecological validity but lacks researcher oversight. Participant non-adherence to requested saliva
sampling regimes leads to inaccurate CAR estimates. Moderate sampling delays of just 8 (5–15) min
between awakening and commencement of saliva sampling are reported to result in over-estimated
CAR magnitude and earlier peaking. This has been attributed to an observed ‘latent’ period in which
cortisol secretion does not increase for up to 10-min after awakening. Replication of this finding
is essential as the findings have considerable implications for CAR research. Healthy participants
(n = 26) collected saliva samples at 5-min intervals for 60 min on 2 consecutive typical weekdays.
Full electronic monitoring of awakening and sampling enabled exclusion of non-adherent data (i.e.,
delays of greater than 5 min between awakening and collection of the first sample). In the 0–15 min
post awakening segment of the CAR a quadratic effect was observed, with no difference between
the awakening and 5 and 10 min samples. Moderate sampling delays will shift assessment of the
CAR just sufficiently along the time axis to not impact upon measurement of the first sample but
to remove the immediate post-awakening latent period from CAR estimates—whilst retaining later
estimates of elevated cortisol secretion. The implication from these results is that accurate CAR
measures can only be determined from data with strict adherence to commencement of saliva sampling
following awakening