Higher cortisol levels at diurnal trough predict greater attentional bias towards threat in healthy young adults

Background Attentional bias (AB), selective information processing towards threat, can exacerbate anxiety and depression. Despite growing interest, physiological determinants of AB are yet to be understood. We examined whether stress hormone cortisol and its diurnal variation pattern contribute to AB. Methods Eighty-seven healthy young adults underwent assessments for AB, anxious personality traits, depressive symptoms, and attentional function. Salivary cortisol was collected at three time points daily (at awakening, 30 min after awakening, and bedtime) for 2 consecutive days. We performed: (1) multiple regression analysis to examine the relationships between AB and the other measures and (2) analysis of variance (ANOVA) between groups with different cortisol variation patterns for the other measures. Results Multiple regression analysis revealed that higher cortisol levels at bedtime (p<0.001), an anxious personality trait (p=0.011), and years of education (p=0.036) were included in the optimal model to predict AB (adjusted R²=0.234, p<0.001). ANOVA further demonstrated significant mean differences in AB and depressive symptoms; individuals with blunted cortisol variation exhibited significantly greater AB and depression than those with moderate variation (p=0.037 and p=0.009, respectively). Limitations Neuropsychological assessment focused on attention and cortisol measurement at three time points daily. Conclusions We showed that higher cortisol levels at bedtime and blunted cortisol variation are associated with greater AB. Individuals who have higher cortisol levels at diurnal trough might be at risk of clinical anxiety or depression but could also derive more benefits from the attentional-bias- modification program.