yogi; in it, Swami Rama demonstrated conscious entry into NREM delta wave sleep through yoga nidra, while a disciple produced delta and theta waves even with eyes open and talking. A therapeutic model was developed by Datta and Colleagues (2017) and the same appeared to be useful for insomnia patients. Datta and colleagues (2022) report a beneficial effect of yoga nidra on the sleep of 45 male athletes, noting that sportsmen often have sleep problems. Their small randomised controlled trial found improvements in subjective sleep onset latency, time in bed, and sleep efficiency with 4 weeks of yoga nidra compared to progressive muscular relaxation (used as the control). Primary research, sometimes on a small scale, has been conducted on various aspects of yoga nidra. One found an association of yoga nidra meditation with increased endogenous dopamine release in the ventral striatum of the brain. The reduced desire for action in the state is associated with the reduced flow of blood in parts of the brain connected with controlling actions, the prefrontal cortex, the cerebellum and the subcortex. Another study reported that yoga nidra improves heart rate variability, a measure of balance in the autonomic nervous system, whether or not it is preceded by a session of hatha yoga asanas. Informal studies have suggested possible benefits of yoga nidra, without the large scale or strictly controlled trials that would be required to demonstrate medical benefit. A study suggested that regular practice of yoga relaxation could reduce tension and anxiety, while autonomic symptoms of high anxiety such as headache, giddiness, chest pain, palpitations, sweating and abdominal pain appeared to respond well. The approach has been used to help soldiers from war cope with posttraumatic stress disorder (PTSD). A 2019 study suggests that yoga nidra can alleviate stress and improve self-esteem of university students. See also Dream yoga Notes References External links Systematic review articles on Yoga Nidra indexed by Google Scholar Sleep Yoga as therapy