Table 6.

Summary of previous HRV-based MDD detection studies.

Authors	Subjects	Test task	Feature Selection	Classification method	ACC
Kuang et al. [18]	MDD 38 HC 38 (female)	Ewing test	Correlation-based method (10 selected)	Bayesian networks 10-fold CV	86%
Byun et al. [19]	MDD 37 HC 41	Mental arithmetic test	SVM-RFE (2 selected)	SVM LOO CV	74%
Minwoo et al. [38]	24a	Multimodal affective contents test	N/A	neuro-fuzzy network with weighted fuzzy membership functions	87%
Roh et al. [9]	23a	N/A	N/A	SVM	71%
Zhang et al. [39]	MDD 10 HC 10	Multimodal affective contents	N/A	Neuro-fuzzy network	95%
Sun et al. [40]	MDD 44 HC 47	Random number generation	N/A	Logistic regression	79%
This study	MDD 40 HC 40	Sleep phase	N/A	BO-ERTC 10-fold CV	86%

Abbreviations: HC, healthy control; N/A, not applicable; CV, cross-validation; ACC, accuracy. ^a Total number of subjects.