Yoga is probably not a treatment that will by itself remove any suicidal impulses, but can be useful in conjunction with other treatments. An issue many people face when feeling suicidal is feeling overcome with life's problems. That generally involves a lot of thought. By removing focus from one's internal dialogue, to that of synchronising movement with breath, yoga is able to provide a break from the constant stream of negative thoughts. It is also good exercise.
Whilst yoga might not be many people's first choice of exercise (it certainly wasn't mine!), especially if they feel they aren't flexible, yoga is actually good on a number of levels. If you are feeling really tired and have no energy, there are gentle yoga classes that will get you moving without too much effort. Yoga is non-competitive, which is really good for anyone with high standards, who is competitive or perfectionist. It is about the journey, not the end goal. And yoga is mindfulness training, which is invaluable for anyone that is feeling depressed.
Classes are available in most major cities - just search the web for a class near you. Try a couple of different teachers and types of classes as there are many styles in yoga. Some brief information on the main types of yoga is below:
Hatha: a very general term that can encompass many of the physical types of yoga. If a class is described as Hatha style, it is probably going to be slow-paced and gentle and provide a good introduction to the basic yoga poses.
Vinyasa, which means breath-synchronized movement, tends to be a more vigorous style based on the performance of a series of poses called Sun Salutations, in which movement is matched to the breath. A Vinyasa class will typically start with a number of Sun Salutations to warm up the body for more intense stretching that's done at the end of class.
Ashtanga (also spelt Astanga), which means eight limbs in Sanskrit, is a fast-paced, intense style of yoga practice. A set series of poses is performed, always in the same order. Ashtanga yoga is very physically demanding, because of the constant movement from one pose to the next, but students progress at their own pace.
Iyengar is a form of Hatha yoga which emphasises alignment and encourages the use of yoga props. It is based on giving primacy to the physical alignment of the body in the poses. In the Iyengar school, it is taught that there is a correct way to do each pose, and that every student will one day be able to attain perfect poses through consistent practice.
Bikram: a series of yoga poses done in a heated room. The room is usually maintained at a temperature of 95-100 degrees. As you can imagine, a vigorous yoga session at this temperature promotes profuse sweating which rids the body of toxins. It also makes the body very warm, and therefore more flexible.
For those living in London, the TriYoga studios have an excellent reputation. It may also be worth checking out classes run by Jane Kersel, who was a visiting lecturer at the Biomedical Trust on the Yoga Therapy Diploma Course where her specialisation was yoga for anxiety and depression.