Your “Circadian Rhythm” is the cycle that your body goes through every 24 hours to form part of your internal body clock. It plays a huge part in sleep, awake/cognitive periods and also mental health.
If your Circadian Rhythm becomes disrupted (which can happen due to lifestyle changes like shift work, medications, illness and other factors like too much exposure to artificial light sources, then sufferers may find their sleeping patterns change, they do not feel alert, they have problems with memory and cognitive functions, and also they may be tired but cannot sleep (insomnia).