Humans follow a 24-hour biological rhythm called the circadian rhythm, controlled by light and darkness of the surrounding environment. This determines the body’s temperature, hormone production and sleep cycles. Circadian disorders are caused due to the disruption of your circadian rhythm by changes in time zones, pregnancy, working in shifts, certain medications and changes in routine activities.

The different types of circadian rhythm disorders include:

• Rapid time zone change syndrome (jet lag): lack of alertness and excessive sleepiness during the day due to travel across time zones
• Shift work sleep disorders: caused if you work in night shifts or rotate shifts
• Delayed sleep phase syndrome(DSPS): caused due to irregular sleep timings, where  you fall asleep late and get up late in the mornings
• Advanced sleep phase syndrome(ASPD): going to sleep early and waking up earlier than desired
• Non 24-hour sleep-wake disorder: occurs in those who are completely blind as the biological clock works with the light and dark cycle. Sleep time and quality are reduced and you may feel sleepy during the day.

Some of the treatments for circadian disorders are:

• Behavior therapy: maintaining regular sleep cycles and avoiding naps, caffeine and nicotine. Minimizing light in the evening and night to manage delayed sleep phase syndrome,and increasing light exposure during evening to control advanced sleep phase syndrome
• Bright light therapy: exposure to a high intensity light for about 1 or 2 hours. This time-critical therapy helps to reset the sleep cycle.
• Cronotherapy: progressive advancement or delay of the sleep cycle. Once the sleep cycle is reset, regularity should be maintained.