Ayurveda ennumerates three important aspect of life that’s called as trayopasthambha ( three basic pillars of life ). It includes Ahara ( food) , Shayana ( sleep ) and brahmacharya ( reduce over indulgence in sex ). Some of the commentators read Brahmacharya with a prefix “aa” that makes the word exactly the opposite of Brahmacharya in sanksrit. Scholars of this opinion says then Trayopasthambas as food, sleep and sex. Taking the sleep in particular, Ayurveda projects its physiology, classification and importance in various contexts. In Charaka samhitha , sleep is classified into six types according to its causative factors. They are , sleep without any external imbalances ( surroundings) , due to depression , due to increased accumulation of Kapha,due to tiredness, due to some chronic debilitating diseases, or due to some external injury or imbalance of doshas.
Sleep in ayurveda is predominantly an aspect of Kapha. It makes Tamoguna (inertia) of mind. The disturbances in sleep is induced by Vata and Pitta. So.. that which promotes kapha without aggravating the Vata and Pitta will be considered as the stimulant of sleep. With this understanding, one can examine the Ayurvedic procedure shirodhara and its impact based on modern physiology of sleep.
Sleep generated and maintained is more of a balance between two systems in the brain. One is the Synergistic effect produced by Hypothalamus to make the body rest, and the other is Circadian rhythm (Biological clock ) coordinated by the Pineal gland with the hormone Melatonin. The procedure Shirodhara impacts these two system by inducing a cooling effect into the brain. There are lotsof studies suggest that the temperature in the brain if drops slightly, can stimulate the secretion of Melatonin. In this way Shirodhara promotes the sleep cycle and thus have a complementary impact to reduce stress.
During Shirodhara , the oils that are using is of Vatahara property. These oils are prepared by saturating it with various fats soluble contents from medicinal plants that have combined effect on controlling Vata. As ayurveda considers neurochemical impulses and brain waves as the feature of Vata , controlling such a hyperstimulated impulses will calm the brain and help to get a stable relaxed sleep. Since these oils are also having a muscle relaxant effect , and is poured directly over the head slowly in a slightly warm . It helps to relax the msucles in the scalp and head that will help to reduce the vascular tension and assure proper blood flow to the brain. Once the blood supply is sufficient, brain will feel more relaxed and the person will be prone to sleep.
There is another widely applied phenomenon called ASMR( Autonomous sensory merdian response ). The exact mechanism behind this phenomenon needs further studies. But the tingling, pleasurable sensation we feel when there is gentle touch over the head is one of the implication of ASMR. Shirodhara also make use of this mechanism to make the brain more comfortable to fall asleep.
Shirodhara thus is a combined effect of all these phenomena. It relaxes the mind-body system and help to get rid off the stress factor there by promises a good stable sleep.