Table 3.

Psychological questionnaires scores, breathing rates, HRV indices at pre-test, post-test, and follow-up for the HRV-BF group (n=18)

Variable	Time			F	p	ηp2	Bonferroni’s post-hoc comparison
	Pre-test (1)	Post-test (2)	Follow-up (3)
BDI-II
Total score	24.06±13.48	13.22±10.52	16.94±15.14	12.89***	<0.001	0.43	1>2, 3
Cognitive depression	17.06±11.84	9.17±8.21	11.83±12.16	12.85***	<0.001	0.43	1>2, 3
Somatic depression	7.00±2.79	4.06±2.69	5.11±3.31	7.46**	0.002	0.31	1>2
BAI, total score	21.11±10.90	11.72±8.10	14.50±11.74	12.32***	<0.001	0.42	1>2, 3
PSQI
Total score	12.28±3.50	9.78±3.69	10.39±4.18	7.45**	0.002	0.31	1>2
Subjective sleep quality (C1)	2.00±0.77	1.39±0.70	1.78±0.81	5.55**	0.008	0.25	1>2
Sleep latency (C2)	1.67±0.91	1.56±0.86	1.72±0.83	0.38	0.690	0.02
Sleep duration (C3)	1.78±1.06	1.22±0.94	1.22±1.06	3.32*	0.048	0.16	1>2
Habitual sleep efficiency (C4)	1.17±1.15	1.06±1.06	0.56±0.92	2.92	0.084	0.15
Sleep disturbance (C5)	1.44±0.51	1.39±0.61	1.56±0.71	0.62	0.542	0.04
Use of sleeping medications (C6)	2.17±1.20	1.78±1.26	2.00±1.37	1.25	0.299	0.07
Daytime dysfunction (C7)	2.06±0.94	1.39±0.85	1.56±0.92	5.14*	0.011	0.23	1>2
Total time spent asleep (min)	28.06±15.82	22.22±13.53	30.17±20.69	3.54*	0.040	0.17	NS
Total sleep time (hr)	5.58±1.59	6.64±1.16	6.59±1.37	7.40**	0.002	0.30	2, 3>1
Sleep efficiency (%)	71.72±15.43	79.17±12.58	86.28±14.03	13.16***	<0.001	0.44	3>1, 2
PSAS
Total score	43.11±13.70	33.83±12.09	38.06±14.02	8.35**	0.001	0.33	1>2
Cognition arousal	24.89±9.07	18.56±7.88	22.11±9.52	7.92**	0.002	0.32	1, 3>2
Physical arousal	18.22±6.37	15.28±5.54	15.94±5.85	3.31*	0.049	0.16
Breathing rate (breath/min)	14.56±4.36	11.02±4.06	11.07±3.63	6.44**	0.004	0.26	1>2, 3
HRV indices
SDNN (ms)	39.80±16.71	49.97±26.92	51.94±25.26	6.57**	0.004	0.28	2, 3>1
LF (ms2)	158.42±233.18	583.46±932.19	676.78±1058.31	5.03*	0.012	0.23
HF (ms2)	147.89±114.23	185.08±182.59	184.85±163.03	0.72	0.497	0.04
ln(LF) (ms2)	4.40±1.23	5.40±1.47	5.64±1.38	10.62***	<0.001	0.38	2, 3>1
ln(HF) (ms2)	4.55±1.22	4.59±1.28	4.75±1.10	0.33	0.724	0.02
LF/HF ratio	1.25±1.39	6.83±11.04	5.29±6.66	2.75	0.098	0.14
Total power (ms2)	596.80±573.68	1,052.27±1,131.51	1,098.48±1,156.35	5.18*	0.011	0.23	2>1

Values are presented as mean±standard deviation.

HRV, heart rate variability; BF, biofeedback; BDI-II, Beck Depression Inventory-II; BAI, Beck Anxiety Inventory; PSQI, Pittsburgh Sleep Quality Index; NS, not significant; PSAS, Pre-Sleep Arousal Scale; SDNN, standard deviation of normal to normal intervals; LF, low frequency; HF, high frequency.

^*p<0.05,

^**p<0.01,

^***p<0.001.