Ma, X., et al. (2017). The effect of diaphragmatic breathing on attention, negative affect and stress in healthy adults. Frontiers in psychology, no. 8, pp. 874, https://doi.org/10.3389/fpsyg.2017.00874. Full text.
From the Abstract. A growing number of empirical studies have revealed that diaphragmatic breathing may trigger body relaxation responses and benefit both physical and mental health. However, the specific benefits of diaphragmatic breathing on mental health remain largely unknown.
The present study aimed to investigate the effect of diaphragmatic breathing on cognition, affect, and cortisol responses to stress. Forty participants were randomly assigned to either a breathing intervention group (BIG) or a control group (CG). The BIG received intensive training for 20 sessions, implemented over 8 weeks, employing a real-time feedback device, and an average respiratory rate of 4 breaths/min, while the CG did not receive this treatment. . . .
The findings suggested that the BIG showed a significant decrease in negative affect after intervention, compared to baseline. . . . In conclusion, diaphragmatic breathing could improve sustained attention, affect, and cortisol levels.