# A Novel Approach for Acute Mental Stress Mitigation Through Adapted Binaural Beats: A Pilot Study
## 4 Discussion  
Given the significant impact of stress on our society, new solutions for its mitigation are necessary. In this regard, BBs may play a significant role, given their convenience and non-invasiveness. Overall, a consensus about their effectiveness is missing, and this is certainly due to missing standardized approaches, methodological issues, and personalized treatments. With this work, we present a different stimulation approach, which takes into account the physiological response of the subject to adapt \(f_{BB}\) and reduce acute mental stress artificially recreated through a modified version of the MAT. To adapt the \(f_{BB}\) in real time, we considered the output of a regressor, which was implemented to recognize a stressful condition. For this reason, the training phase was pivotal. The outcomes of that phase, which are reported in Figure 3, highlight that the protocol was capable of inducing acute mental stress in the participants. Indeed, both the average heart rate and the VAS outcome resulted in higher values compared to the relaxing condition, as expected [17]. The \(RR\) interval played a significant role, as evidenced by the  
Figure 6: (**A**) Average stress indexes from all the participants considering steps 3, 4, 5, and 6. (**B**) Results of the VAS questionnaire. (**C**) Accuracies of the MATs during CBB and ABB simulations. (**D**) Reaction times of the MATs during CBB and ABB simulations. Statistically significant differences are indicated with \({}^{*}\) for \(p<0.05\). Figure 7: (**A**) Average stress indexes with pairwise comparison for CBB and ABB simulations. (**B**) Comparison of the average heart rates. (**C**) Comparison of the root mean square of successive differences (RMSSD). Statistically significant differences are indicated with \({}^{*}\) for \(p<0.05\). Observe that one particular subject exhibits behavior contrary to the trend seen in the others; this deviation is highlighted by the red segments. ranking of the different features (as shown in Figure 4A), followed by others that manifest changes during acute mental stress conditions, e.g. \(RT_{R}\)[41] and the QT interval [40,48]. Despite the significance of the \(RR\) interval, Figure 4 highlights the variability among subjects in feature importance, showing that other features, such as \(RT_{R}\), may prevail over \(RR\) in recognizing a stressful condition. This underlines the importance of a subject-specific approach, taking into account the physiological response of the users. The importance of adapting to the user can be appreciated also in Figure 5, where the changes over time of the stress predictor (\(S\)) are reported. By constantly changing \(f_{BB}\) on the users' response, lower values of \(S\) were obtained, regardless of the stimulation order. The significance of modulating the stimulation on the user's physiological response is highlighted in Figure 5C, where no consistent trend in \(f_{BB}\) over time is evident among subjects, and high variability occurs. A comparison among the average stress indexes of steps 3 to 6 of the experimental protocol (see Figure 1B) can be appreciated in Figure 6A. The results align with Figure 5A,B, indicating a statistically significant reduction in the average stress index during the ABB stimulation. Surprisingly, no statistical difference was detected in the comparison of the VAS questionnaires after ABBs and CBBs. In this regard, some considerations should be made. Questionnaire are surely a rapid and cost-effective method of data collection [17], but care should be taken because they are not entirely reliable due to a large subjective component and social desirability bias (i.e., the propensity to over-report more desirable attributes while under-reporting socially undesirable activities [49]). The previous considerations, along with the limited sample size, may be the reason for the missing significance in the comparison. Concerning the MAT performances, no statistical difference was detected in either accuracies or reaction times.