Higher Inhalation/Exhalation Ratio during Spontaneous Breathing Associates to Poor Mental Health in University Students

Background Breathing exercises, particularly those involving altered inhalation/exhalation duration ratios (I/E ratios) and increased abdominal movement, have demonstrated the potential for alleviating symptoms of mental health issues. However, it remains unclear which approach is more effective. This study aims to examine how resting respiratory patterns (e.g., I/E ratios and abdominal movement) relate to mental health, potentially guiding psychologists in recommending tailored breathing exercises. Methods A total of 240 university students (120 male and 120 female) were recruited by systematic sampling. The I/E ratio and the contribution of abdominal movement to the sum of abdominal and thoracic movements AM/(AM + TM) were recorded by respiration belts, while depression, anxiety, and stress levels were assessed with the DASS-21. Data were analyzed for each gender; each gender being categorized into either a low or high level symptom category. Results Women with high stress symptoms exhibited significantly lower I/E ratios (a lower I/E ratio indicates breathing with relatively shorter inhalation and longer exhalation) compared to those with lower stress symptoms (n = 117, F  = 4.198, p  = 0.043, ηp² = 0.035). A negative correlation was observed between I/E ratios and depression in women (n = 117, r = -0.211, p  = 0.023). For students with high anxiety symptoms, I/E ratios were negatively correlated with anxiety scores in both men (n = 61, r = -0.292, p  = 0.022) and women (n = 70, r = -0.392, p  < 0.001). There were no substantial correlations between abdominal movement and mental health. Conclusions In general, university students who exhibit relatively shorter inhalations and longer exhalations tend to have poorer mental health, especially among women; This respiratory pattern may represent an autonomic compensatory strategy for coping with psychological distress. More attention could be devoted to breathing exercises involving altered I/E ratios as part of mental health management programs.