The summer solstice has arrived! If you live north of the equator, that means Tuesday and Wednesday will be the longest days of the year in terms of sunlight. But not everyone is celebrating.

For people who suffer from sleep disorders, the summer solstice is a harbinger of worse-than-usual sleep. That's because exposure to sunlight inhibits the secretion of a hormone, melatonin, that promotes sleep and regulates your sleep cycle. More sun means less melatonin, which means a higher chance of tossing and turning at night.

Though there are several factors that contribute to sleep disorders, including allergies, chronic pain, and gastrointestinal problems, one of the more common causes of conditions such as insomnia is endocrine dysfunction, according to the National Sleep Foundation. Problems with the endocrine system, which regulates hormone secretion, can lead to lower levels of melatonin.

That issue is exacerbated on the summer solstice, Dr. Karl Doghramji, medical director at the Jefferson Sleep Disorders Center, told CBS Philly.

"Light antagonizes melatonin," Doghramji said. "Because of that we don’t sleep as well. Melatonin is important for sleep but it is not being secreted until later into the night."

But there are steps people can take to stimulate melatonin secretion, he said. Blacking out your windows and eating foods rich in vitamin B-6, magnesium, and calcium are some natural ways to increase melatonin production.