World Sleep Day 2023 is on March 17th. World Sleep Day is an annual event that is celebrated on the Friday before the Spring Equinox in the Northern Hemisphere. The day aims to raise awareness about the importance of sleep and the impact that sleep has on overall health and well-being.
We are all familiar with the three states of daily experience: 1)Waking 2) Dreaming and 3) Dreamless Sleep.
Let us focus on issues related to sleep and mental health, in the perspective of ancient philosophy as well as the impact of technology on sleep patterns.

Delta (0.5-3.0 Hz): The deep sleep Wave.
The Delta frequency is the slowest of the frequencies and it is experienced in deep, dreamless sleep and in very deep, transcendental, meditation where awareness is completely detached. Delta is the realm of the unconscious mind. It is the Gateway to the Universal mind.
What Vedanta Says about Dreamless Sleep 😴
BRRihadAraNyaka Upanishad IV.3,9: Says as below 👇
When he dreams, he takes away a little of the impression of this all embracing world (the waking state), himself puts the body aside and himself creates a dream body in it’s place, revealing his own lustre by his own light and dreams. In this state, the man himself becomes the light.
Let us know more on the Deep Sleep state according to VEDANTA.
The Deep Sleep state (SuShupta~SU=Sundar/excellent +sUpta=Sleep) ~ prajNa and antaryAmin.
In this state, waking world and dreaming world temporarily ceases. We exist here in non dual state. Most refreshing state. A state of Bliss(with ignorance). In the waking and dreaming state, we are diverted from this state of bliss, though knowledge of our true nature is absent here. All the perceived limitations are removed in this temporary state but ready to spring forth as soon as we move to waking world.
In that sleep state, not for anything desirable does one have any desire.(यत्र सुप्तो न कञ्चन कामं कामयते). Not the slightest trace of dream does it see in that state of deep sleep.(न कञ्चन स्वप्नं पश्यति तत् सुषुप्तम् ). In the sphere of deep sleep, there is just one ” homogenous mass of consciousness” alone (सुषुप्तस्थान एकीभूतः प्रज्ञानघन). Because of his union with the Self and his unbroken knowledge of it, he is filled with joy, he knows his joy, his mind is illuminated (एवानन्दमयो ह्यानन्दभुक् चेतोमुखः). Such is the called third quarter called prajNa (चेतोमुखः प्राज्ञस्तृतीयः पादः).
This dreamless sleep is a causal state of mind. Here all operations of the mind are completely hushed. Even ego-consciousness becomes lost. We don’t know what we are. A king is no king or a beggar is no beggar in this state. In Deep Sleep we have no will, no fear, no worries. But when we emerge into a waking state, all operations of restless minds start.