Table 3.

Effect Size and Quality Ratings Using the Scale for Assessing Scientific Quality of Investigations

Reference	Study design	Intervention/duration	Effect size	SASQI score (average)*
De Zeni and Araujo69	Pre–post	Deep breathing (10 min)	dCCQB = 1.026	8/21
			dVAS = 0.968
Eddie et al.39	Controlled trial	HRVB (3 weeks)	dppc2 = 0.232	14.5/21
McClernon et al.67	Crossover trial	Controlled breathing (4 h)	d = 1.498	8/21
Meule et al.18	RCT	HRVB (4 weeks)	dppc2 = 0.727	14/21
Penzlin et al.40	RCT	HRVB (2 weeks)	dppc2 = 0.074	14/21
Shahab et al.68	RCT	Yogic breathing (24 h)	dpost = 0.728	15/21
			d24hr = 0.413
Zucker et al.66	RCT	Portable HRVB (4 weeks)	dppc2 = 0.329	11.5/21

^*Average SASQI scores rated independently by two authors.

CCQB, cocaine craving questionnaire-brief; D, Cohen's d; d_ppc2, effect size based on pooled pretest standard deviation; HRVB, heart rate variability biofeedback; RCT, randomized controlled trial; SASQI, The Scale for Assessing Scientific Quality of Investigations; VAS, visual analog scale.