This is a very common condition that indicates an inability to either fall asleep easily or to sleep without constantly waking up. Sleep is obviously a fundamental biological cycle that can be affected by many different triggers.
Some people are prone to insomnia as a result of stress that creates an overstimulation of the hormonal and nervous systems. This may especially be the case with those who are already chronically ill or under emotional strain. Other common triggers include physical pain, depression, shift work, nutritional issues (ie low blood sugar), medication side-effects and environmental pollution
Insomnia is even more common in older people and can easily be perpetuated by anxiety. It can lead to fatigue, immune suppression, poor concentration and relationship difficulties. In children it may sometimes be linked to poor growth.