The Relationship Between Metacognitive Beliefs and Salivary Cortisol, BDNF, and NDNF Levels: A Cross-Sectional Study

Purpose: The main objective of this study is to non-invasively investigate the relationship between metacognitive beliefs and cortisol, the primary stress output of the hypothalamic-pituitary-adrenal (HPA) axis, as well as neurotrophic factors associated with neuroplasticity brain-derived neurotrophic factor and neuron-derived neurotrophic factor (BDNF and NDNF). Within this framework, the hypotheses that negative metacognitions would be associated with increased cortisol and decreased BDNF levels, and that cortisol might play a mediating role in this relationship, were tested. Method: The study was designed in a cross-sectional model with 60 university students. Participants' metacognitive beliefs were measured using the Metacognitions Questionnaire-30 (MCQ-30). Salivary cortisol, BDNF, and NDNF levels were analyzed using the ELISA method. Pearson correlation and hierarchical multiple regression analyses were used for data analysis. Finding: The results showed a significant positive relationship between the total metacognition score and cortisol (r = 0.589, p < 0.01) and a strong negative relationship between cortisol and BDNF (r = −0.662, p < 0.01). Hierarchical regression analysis supported a partial mediation model, indicating that dysfunctional metacognitive beliefs have both a significant direct negative association with BDNF and an indirect association mediated by cortisol. In the final model, both metacognition (β = –0.298, p < 0.05) and cortisol (β = –0.281, p < 0.05) were significant factors associated with lower BDNF levels. NDNF showed a positive relationship with BDNF (r = 0.571) but not with other variables. Conclusion: These findings point to a psychobiological model where dysfunctional metacognitive beliefs are linked to suppressed neuroprotective mechanisms like BDNF, both directly and indirectly through HPA axis activation. The results shed light on the potential neurobiological mechanisms underlying the effectiveness of metacognitive therapies.