StressLess Dog-Assisted Activities and Segmental Hair Cortisol in University Students During Examinations: A Quasi-Experimental Study

University dog-assisted activities may contribute to student well-being, yet less is known about their relationship with physiological indicators that integrate longer time periods. This study examined the association between participation in the University of Granada StressLess program and segmental hair cortisol concentration (HCC) during examination periods. Participants were 64 students: 34 from the University of Granada who completed three group sessions with dogs as part of StressLess and 30 from the University of Extremadura (Badajoz campus) who did not participate in the program. A single lock of hair was collected from each participant after examinations, in January and June 2026, respectively, and two adjacent 2-cm segments were analyzed by immunoassay. The proximal-minus-distal difference (A−B) was −0.47 pg/mg in StressLess and +0.80 pg/mg in the comparison group. The primary between-group comparison significantly favored StressLess: −1.27 pg/mg (95% CI: −2.39 to −0.15; p = 0.027; Hedges’ g = −0.57). Sensitivity analyses were consistent in direction. The finding is compatible with a beneficial contribution of the program to the profile of cumulative cortisol exposure. These exploratory results support further evaluation using concurrent groups and randomized allocation. Preprint v1.0. This manuscript is under consideration at Anthrozoös and has not undergone peer review.