Salivary cortisol responses on the Trier Social Stress Test-Online based on smoking habits and resilience scores

In Japan, alcohol, tobacco, coffee, and tea are categorized as “Shikohin” (i.e., non-nutritious items consumed for flavor). I hypothesized that participants with high resilience and strong smoking habits would show blunted cortisol responses to the Trier Social Stress Test-Online (TSST-OL). Participants (N = 41) were classified into four groups based on the degree of smoking (≤ 14 or ≥ 15 cigarettes per day) and the median total score on resilience scales (low-resilience low-smoking, low-resilience high-smoking, high-resilience low-smoking, and high-resilience high-smoking). Participants completed the TSST-OL, measuring subjective stress and salivary cortisol, at eight time points. A two-piece multilevel growth curve model with landmark registration (GCM-LR) examined the effects of smoking habits and resilience scores on cortisol concentrations. Blunted cortisol responses were similarly present in all four groups; thus, my hypothesis was unsupported. All groups showed similarly elevated subjective stress responses. GCM-LR results showed no significant cortisol increase, but the fixed effect of cortisol recovery was significant. The likelihood ratio test showed that the random effect of resilience scores was significant. Habitual smokers do not have an elevated cortisol response, even in stressful situations. Substantial individual differences were suggested in the effect of resilience scale scores on cortisol concentration.