Daylight Saving Time was introduced so during World War One as a way of conserving fuel needed for war industries and of extending the working day so people could use less energy. The resulting sleep disturbance, however, can take a toll on your body and wreak havoc on your internal clock.

Opinions are mixed when it comes to the time changes twice a year, as well as the potential impact on public health. In fact, Arizona (except the Navajo region), Hawaii and the overseas territories of the United States don’t observe DST, and some states have petitioned to permanently end it. Reasons cited vary from getting more sun, to altered sleep patterns and increased road accidents.

Experts point to several possible causes for the troubles, including trouble adjusting to the sudden sunset time change.

To compile the following list of health effects DST may have on a person’s health, 24/7 Wall St. reviewed over a dozen studies and consulted a sleep expert.

Click here to see the ways DST could affect your health.

The most common time change disorder is circadian rhythm disorder, a disruption in the body’s internal clock due to DST or jet lag, according to Dr. Jordan Stern, board certified in Otolaryngology and Sleep Medicine and founder of Blue Sleep. “Moving the clock forward is always more difficult; in travel this translates into more difficulty when traveling East than when traveling West.”

Adapting to new time zones usually takes the body about one day per hour of time difference, but some studies show effects lasting up to 10 weeks. Other research goes even further, indicating that the circadian system does not adjust to DST at all, and its seasonal adaptation to shorter days and longer nights is disrupted by the introduction of summer time. The result is your body follows one clock while your social calendar follows another.

The one-hour change can seriously impair cognitive and motor function, especially in sleep-deprived populations, said Stern. Because natural blue light is the strongest factor in controlling the internal clock, rising 15 minutes earlier for four days, and turning on blue light (from your computer or phone in the morning) will definitely help wake you up in the morning, he added. “For falling asleep at the right time a few days before DST hits, 2 mg of Melatonin (not more!), 2 hours before bedtime can help.” Warm baths, chamomile tea, and reading a book are other helpful strategies for winding down at night, Stern added.