Ever wonder why you are sleepy at 6 p.m. in the wintertime than you are during the summer months? It might be because your circadian rhythms are disrupted.

Circadian rhythms are the body’s mental, physical, and behavioral changes to the 24-hour cycle of daylight and darkness. Also known as the sleep/wake cycle, the circadian rhythm regulates the body’s response to day and night, helping you stay awake during the day and get to sleep at night.

Circadian rhythms work somewhat in tandem with the body’s “biological clock,” which controls the production of melatonin. Melatonin is the “sleep hormone” that is naturally produced by the body. Levels of melatonin typically rise in later in the evening, roughly as the sun begins to set and your eyes begin to sense darkness. Those levels of melatonin remain high overnight, and then begin dropping near dawn.

Light inhibits melatonin production—that includes daylight or light from electronic devices or bedside lamps. Even being around bright lights too close to bedtime can affect the ability to fall asleep.

Circadian rhythms can be especially challenging for someone who suffers from what’s known as “circadian rhythm disorder.” That disorder can occur either because the body’s internal (biological) clock is off, or because of outside factors such as shift work, travel, especially when crossing time zones or other demands of life. For these people, light therapy can come in handy to help teach the body’s internal clock how to function again. Light therapy would involve the use of bright lights early in the morning to reset your clock. There are devices such as the “Retimer” or the “Human Charger”.

Regular sleep habits and good sleep hygiene can help keep circadian rhythms in check. Having a regular schedule of going to sleep and getting up in the morning the same time each morning, even on weekends, along with having the ideal sleep environment—a cool, dark room—can also help you get the best night’s sleep. The room should also be free of noise and gadgets that generate electromagnetic frequencies, including computers, televisions, cellphones, tablets, games, etc. Electromagnetic frequencies interrupt the normal neurochemistry in the brain and block the ability of the body to fall asleep and to get into a deep sleep.

Circadian rhythms affect all humans and other mammals. Even though mammals such as bears are more susceptible to the shorter days of winter, entering into a state of less activity, a sort of hibernation, the circadian rhythm is still functional. Bears evolutionally have developed the ability to hibernate for months without food and water as a means of survival during the winter months when food is sparse. Humans, of course, is clearly don’t have the luxury of taking it easy all winter long, waking only periodically to grab a bite to eat (like ground squirrels do). The inability to regulate your circadian rhythm may be the sign of a much larger problem, such as depression.

If you or someone you know drags to get through a day, you may need help regulating your sleep with solutions for better sleep hygiene, psychoemotional needs, or even improving nutrition. It’s also a good idea to be checked for sleep-disordered breathing, potentially a physiological cause for your sleep disruptions. That may require a solution involving the correction of an oral-structural imbalance, or an obstruction in the airway, the one component of sleep that is best addressed by a qualified oral physician.

Also, consider wearing blue blocking glasses at night if you find the need to be on your phone, computer or electronic devices. The constant exposure to bright lights and electromagnetic frequencies slows the production of melatonin.