In this article, we discuss sleep disorders such as somnambulism and somniloquy from an occult perspective. There are supposed to be five concentric sheaths in our consciousness and during sleep, the subtle sheaths eject themselves from the gross physical sheath to travel in their corresponding subtle realms, as was discussed in an earlier article on Explaining out-of-body and near-death experiences. Some sleep disorders can be attributed to the irregularity in the manner in which these sheaths interact with each other during sleep.
Based on empirical scientific evidence, sleep-walking is said to be precipitated by sleep deprivation, fatigue and fever and intake of drugs, especially sedatives, hypnotics, antipsychotics, stimulants and antihistamines. It is most prevalent amongst children and decreases with age. It has been observed to occur during the slow-wave sleep stage; this is the stage of sleep in which mental performance is most impaired and no dreams are said to occur. There even seems to be a genetic component to this disorder. Medical science has developed various theories regarding sleep-walking and preliminary information regarding these theories can be obtained in [1, 2].
Now onto the occult perspective. According to the Mother Mirra Alfassa, somnambulism occurs when the astral body, which has gone out of the physical body during sleep, drags the physical body along with itself. Normally, when we fall asleep, the astral body (subtle body) ejects from the physical body and travels in its corresponding subtle world. There is a silver cord which maintains the bond between the astral and physical bodies. What happens during sleep-walking is that the physical body consciousness, enfeebled due to fatigue, is incapable of resisting the astral body’s influence and consequently, involuntarily moves along with the latter.
Question: At times when one goes out of the body, the body follows the part which goes out.
Mother Mirra Alfassa: You are speaking of a somnambulist? But that is quite another thing. This means that the part which goes out (whether a part of the mind or a part of the vital) is so strongly attached to the body, or rather that the body is so attached to this part, that when this part decides to do something the body follows it automatically. In your inner being you decide to do a certain thing and your body is so closely tied to your inner being that without thinking of it, without wanting to do so, without making any effort, it follows and does the same thing. Note that in this matter, the physical body has capacities it would not have in the ordinary waking condition. For instance, it is well known that one can walk in dangerous places where one would find it rather difficult to walk in the waking state. The body follows the consciousness of the inner being and its own consciousness is asleep – for the body has a consciousness. All the parts of the being, including the most material, have an independent consciousness. Hence when you go to sleep dead tired, when your physical body needs rest absolutely, your physical consciousness sleeps, while the consciousness of your subtle physical body or your vital or of your mind does not sleep, it continues its activity; but your physical consciousness is separated from the body, it is asleep in a state of unconsciousness, and then the part which does not sleep, which is active, uses the body without the physical consciousness as intermediary and makes it do things directly. That is how one becomes a somnambulist. According to my experience, the waking consciousness goes to sleep for some reason or other (usually due to fatigue), but the inner being is awake, and the body is so tied to it that it follows it automatically. That is why you do fantastic things, because you do not see them physically, you see them in a different way. 
Question: How can one be cured of somnambulism?
Mother Mirra Alfassa: Quite simply, by putting a will upon the body before going to sleep. One becomes a somnambulist because the mind is not developed enough to break the inner ties. For the mind always separates the external being from the deeper consciousness. Little children are quite tied up. I knew children who were quite sincere but could not distinguish whether a thing was going on in their imagination or in reality. For them the inner life was as real as the external life. They were not telling stories, they were not liars; simply the inner life was as real as the external life. There are children who go night after night to the same spot in order to continue the dream they have begun – they are experts in the art of going out of their bodies. 
Sleeptalking is said to be prevalent amongst children and also found to occur in fatigued adults. According to the Mother Mirra, this occurs because the mental sheath does not travel out of the body as it normally would during dreams.
Question: Sweet Mother, At times I talk in my sleep. It is a sign that the mind lacks control, isn’t it? So what should I do to keep it quiet at night?
Mother Mirra Alfassa: Generally when the body is asleep at night, the mind goes out because it is difficult for it to remain quiet for a long time; and that is why most people do not talk.
But your mind seems to remain in your body, so you must ask it to remain perfectly quiet and silent so that your body can rest properly. A little concentration for that, before going to sleep, will surely be effective. 
Related (and unrelated) Posts
- Towards more conscious sleep and dreams
- Perception of Time changes with the concentration of consciousness
- The existence of vital signs during sleep or coma
- Why one should not hate the sinner?
- Sri Aurobindo and the Mother on Astrology
- Sri Ramakrishna’s occult contact with Sri Aurobindo
- Ramana Maharshi on World War II
- Silviu Craciunas has a dream of Sri Aurobindo
- Spirituality : between morality and immorality
- Hermeneutics: how to read holy scriptures
- Why Do Some People Sleepwalk? in the Ask the Brains column of the Scientific American Mind »February 2008 (accessed Dec 15, 2010)
- Sleepwalking wikipedia . (accessed Dec 15, 2010)
- Collected Works of the Mother, vol 16, p 400.
- Collected Works of the Mother, vol 4, pp 127-128.