It has been shown to cause the brain to produce less of it, when supplemented, and accordingly , should not be used on more than a very short term basis: a few times, at most, but I wouldn't recommend even that. Rather, use the following: Exercise, but not within 2 hours of bedtime. Have a warm bath, or shower, an hour before bedtime, then a glass of very warm milk, possibly with Horlicks, or one of the herbal teas, below, and use dimmer lighting. Put your mind in a position where it wants to shut itself off, and sleep. See insomnia treatments, in much more detail than can be included here, in section 3, at ezy build, below. Use one of the relaxation methods, in bed, after lights out, on pages 2, 11, 2.c, or 2.i, but they can take some time to learn, (progressive muscular relaxation excepted) so learn and become proficient in their use during the day.
An alternative is to use the EFT, in section 53, and pages 2.q, and 2.o, saying to yourself: "Even though I currently have a sleep disorder, I deeply and completely accept myself." (or choose your own wording) while you use the acupressure tapping. Some more; quick, and easy to learn, are at
http://www.umm.edu/sleep/relax_tech.htm The progressive muscle relaxation, (most easily learned) guided imagery, and mindfulness breathing are known to be effective, although I haven't tried the other 2 methods.
Find out which works best for you, in the daylight hours, so you will be prepared, come bedtime. For many people, a good idea is to develop a set "wind down" routine for the last hour before bedtime, so your subconscious mind learns that it is time to put thinking aside, and prepare for mindfulness, (awareness, without cogitation/purposeful thought) or the EFT, in preparation for sleep, but the idea with mindfulness is to not even think about sleeping: just drift off, naturally, during exercising those techniques.
Avoid TV, computer, or anything exciting in this hour, although reading a BORING! book is a good idea. I suggest that you try using the EMDR variant, below, prior to the mindfulness, or the progressive muscular relaxation, but after the EFT, if that method is chosen. Experiment, to find which combination works best for you.
(The following is a variant of Eye Movement Desensitisation Reprocessing therapy, which has been used successfully for those people suffering from Post Traumatic Stress Disorder, insomnia, and anxiety: it is easily learned, quick to use, yet can be very effective. It is easy to be dismissive of such a seemingly unusual technique, but give it a good tryout, for at least a few weeks, to see if it is effective in your case).
Prior to using either of the methods in the above paragraph, first sit comfortably, and take a deep breath. Then, without moving your head, move your eyes from the left, to the right, and back again, taking around a second to do so (say: "a thousand and one": this takes approximately a second).
Repeat this procedure (without the words, although you can count, subvocally, if you like) 20 times: "A thousand and one; a thousand and two... " and so on, to a thousand and twenty. Then close your eyes and relax. Become aware of any tension or discomfort you feel.
Then open your eyes, and take another deep breath, and repeat step one, closing your eyes, and relaxing afterwards, in the same manner. Then, repeat the procedure one last time. Some people may find that this is all they need do.
With experience, you may find that you can practise this in public, with your eyes closed, which greatly widens the window of opportunity for its use, and avoids attracting unwanted attention. I have found that the 2 - 3 minutes spent using the EMDR markedly reduces distractions to the relaxation process, and is repaid many times over.
I also use it prior to my chosen relaxation technique, after lights out, at night. For more about Eye Movement Desensitisation & Reprocessing therapy, showing recommendations by those who have used it, including a professional psychotherapist with more than 20 years of experience in that field, see sections 33 - 34, at ezy-build.
Usually, I have a cup of chamomile herbal tea, an hour before bedtime, and employ many of the techniques in section 3. Others may prefer Sleepytime, by Celestial Seasonings, Relax, Be Sleepy, or valerian root, from supermarket tea, or health food aisles.
http://www.ezy-build.net.nz/~shaneris 
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