Neural responses to acute stress predict chronic stress perception in daily life over 13 months

The importance of amygdala, hippocampus, and medial prefrontal cortex (mPFC) for the integration of neural, endocrine, and affective stress processing was shown in healthy participants and patients with stress-related disorders. The present manuscript which reports on one study-arm of the LawSTRESS project, aimed at investigating the predictive value of acute stress responses in these regions for biopsychological consequences of chronic stress in daily life. The LawSTRESS project examined law students either in preparation for their first state examination (stress group [SG]) or in the mid-phase of their study program (control group [CG]) over 13 months. Ambulatory assessments comprising perceived stress measurements and the cortisol awakening response (CAR) were administered on six sampling points (t1 = − 1 year, t2 = − 3 months, t3 = − 1 week, t4 = exam, t5 =  + 1 week, t6 =  + 1 month). In a subsample of 124 participants (SG: 61; CG: 63), ScanSTRESS was applied at baseline. In the SG but not in the CG, amygdala, hippocampus, and (post-hoc analyzed) right mPFC activation changes during ScanSTRESS were significantly associated with the trajectory of perceived stress but not with the CAR. Consistent with our finding in the total LawSTRESS sample, a significant increase in perceived stress and a blunted CAR over time could be detected in the SG only. Our findings suggest that more pronounced activation decreases of amygdala, hippocampus, and mPFC in response to acute psychosocial stress at baseline were related to a more pronounced increase of stress in daily life over the following year.


Ambulatory assessment (AA)
The AA was carried out with the combined smartphone app and web platform movisensXS (version 1.3.2 to 1.5.13;movisens, Karlsruhe, Germany).For the MRI sample, it comprised an assessment of perceived stress levels ten times a day, a short morning and evening questionnaire, and the collection of three saliva samples after awakening for later assessment of the CAR.
Item wording was predominantly based on existing questionnaires (Positive and Negative Affect Schedule 1 ; Multidimensional Mood State Questionnaire 2 ; State-Trait Anxiety Inventory 3 ), or research papers 4 .Exploratory factor analyses of 10.0% of the surveys of the entire LawSTRESS sample (1613 out of 16430) revealed a one-factor-solution with the five items "time pressure", "relaxed", "tense", "overstrained", and "disappointed with the own performance".Subsequent confirmatory factor analyses of all surveys showed good fit indices (all CFI > .99;all RMSEA < .15).Thus, for all analyses the five-items AA stress scale was used.At t1, t2, t5, and t6, the AA was conducted on two consecutive working days while at the sampling points close to or during the examination days (t3 and t4), it took place on single days only.T4 in the SG (not in the CG) was carried out at the weekend between the eight-days exam period.The first daily query took place immediately at the individually chosen awakening time between 5:00 and 7:30 a.m. and the last one at 9:00 p.m.The remaining queries were presented at pseudo-randomized times between 8:30 a.m. and 8:00 p.m. with a minimum interval of 60 minutes between two queries.Across all measurement points, we collected 100 queries per participant.Those who did not have a compatible Android smartphone were equipped with a device provided by the institute.
The CAR was assessed on both sampling days at t1 and on the first day of each AA phase at the remaining timepoints.Saliva samples were collected immediately after waking as well as 30 and 45 minutes later using Cortisol Salivettes  (Sarstedt, Nuembrecht, Germany).Participants were instructed not to drink (except from water), eat, smoke, or brush teeth during the first 45 minutes after awakening.To increase compliance and sampling accuracy, functional and non-functional MEMS caps from the company AARDEX Ltd. (Zug, Switzerland) were used in 61.9% -77.2% (varying over sampling points) of the measurements 5,6 .In addition, a random three-digit code was presented with the 2. Supplementary results

ScanSTRESS: neural responses
Table S1.Activated and deactivated structures under psychosocial stress (two tailed combined FWEcorrected for whole brain, threshold < .05)including z-and p-values as well as the localization of peak voxels.
Note. k = cluster size in voxels; MNI = Montreal Neurological Institute; global cluster maxima are in boldface.

Figure S1 .
Figure S1.Time course of mean perceived stress levels (±SEM) in the stress (SG) and control group (CG) over the study period.Note.t = timepoint; t1 = one year before the exam, t2 = three months prior exam, t3 = one week prior exam and t4 = in the middle of the exam period.

2. 3 .
Figure S2.Time course of the AA stress scale (±SEM) in the stress group.For illustrative purposes, participants were divided into three groups of equal size according to their right mPFC response.Note.t = timepoint; t1 = one year before the exam, t2 = three months prior exam, t3 = one week prior exam and t4 = in the middle of the exam period.

Figure S3 .
Figure S3.Mean cortisol values (±SEM) for the stress group over the study period.Note.t = timepoint; t1 = one year before the exam, t2 = three months prior exam, t3 = one week prior exam, t4 = in the middle of the exam period, t5 = one week after the exam, and t6 = one month after the exam.

Table S2 .
Parameter estimates for overall effects for the final perceived stress model.

Table S3 .
Parameter estimates for overall effects of the final model for the cortisol awakening response in the stress group.