Why am I always tired?
Why can't I sleep at night?
Why do I suffer from jetlag?
We all have a body clock, a biological structure that controls how we feel, our mental and physical performance, and whether we are active or asleep. This is nature's response to our rhythmic environment, dominated by the sun, light and dark. Though the body clock normally adjusts us to daytime activity and night-time sleep, it can go wrong - producing some forms of insomnia and even depression. It can also be tricked by changes in our lifestyle causing jet lag or the malaise of night-workers.
The...