The effect of chiropractic manipulation on salivary cortisol levels

Background: The stress response in humans is a healthy response and is necessary for life. The effects of chiropractic manipulation (CM), if any, on stress are ill-defined. Cortisol has been used as an accurate measure of the stress response system in humans. Salivary cortisol is a noninvasive technique to accurately quantify biologically active cortisol. Objective: To determine whether basal salivary cortisol levels can be properly detected and whether CM has any direct effect on basal salivary cortisol levels in humans. Methods: Subjects were adult male students attending a chiropractic college. Salivary samples were collected for 5 weeks. During Week 1, samples were collected by the students at home upon waking. During Weeks 2 through 5, home samples were collected upon waking and were followed by an additional time course of samples collected in a laboratory setting before and after CM. Salivary cortisol was measured by enzyme-linked immunoassay. Results: Chiropractic manipulative therapy did not significantly change basal salivary cortisol levels. The time course of acute changes to cortisol levels was independent of testing week and group. A decrease in salivary cortisol was detected over time on each trial testing day. Overall, cortisol levels significantly decreased from the time of the home samples until the pretreatment laboratory measurement (P < .05). Cortisol levels subsequently decreased from pretreatment to 15 minutes after treatment (P < .05). After treatment, there were progressive decreases in cortisol levels from the 15- and 30-minute time points to the 60-minute time point (P < .05). Conclusion: The results of this pilot study suggest that there is no effect of CM on salivary cortisol levels in asymptomatic subjects. As such, we conclude that neither the anticipation of CM nor the spinal manipulative procedure itself induces a state of stress or anxiety.