GERD, or gastroesophageal reflux disease, can cause symptoms that aren't quite apparent until you lie down to try to fall asleep.

"When lying down, it’s easier for stomach acids to flow up your esophagus, causing heartburn," Terry Cralle, RN, clinical sleep educator and sleep consultant for Saatva, tells Bustle. "Heartburn, in turn, can disrupt falling and staying asleep. That’s why many people with GERD experience an increase in symptoms at nighttime and may have trouble finding a comfortable position for sleeping." Avoiding GERD trigger foods like spicy food, coffee, and alcohol, in the hours before bed, may provide some relief.

Anxiety doesn't exist solely in the mind. If you've been dealing with feelings of stress and nervousness in your daily life, it may be building up and causing it to be difficult for you to fall asleep.

"Those who experience anxiety have a complex relationship with sleep," Dr. Sujay Kansagra, Mattress Firm’s sleep health expert, tells Bustle. "Anxiety can not only prevent someone from falling asleep but it can also be worsened once a person experiences the effects of sleep deprivation." Dr. Kansagra recommends talking to your doctor if stress or anxiety may be affecting your ability to fall asleep.

If falling asleep regularly takes more than 20 minutes for you, and you also experience respiratory symptoms, this could be caused by asthma.

"Asthma symptoms often worsen at night, [including symptoms of] nighttime coughing, chest tightness, wheezing and breathlessness: a condition referred to as 'nocturnal asthma,'" Cralle says. Check in with your doctor if you realize that these sorts of symptoms tend to come along at night.

Keeping a completely different sleep schedule on weekdays and weekends can make falling asleep more difficult in general.

"Another major factor that may contribute to longer sleep latency is 'social jetlag,' brought on by the shift in sleep schedules that many experience on days off compared to workdays," Heneghan says. This issue with your circadian rhythm can be addressed by keeping a more consistent bedtime and wake up time throughout the week.

If you have general aches and pains, and they worsen at night enough to make it difficult for you to fall asleep — you may have undiagnosed arthritis. And arthritis doesn't only affect older people.

"It is estimated that as many as 80 percent of people with arthritis have difficulty sleeping," Cralle says. "Pain makes it hard to get comfortable and to fall — and stay — asleep. Since sleep deprivation makes pain worse, it's critical that arthritis sufferers get enough quality sleep." So talking with your doctor both about your pain and your sleep problems can be a step in the right direction.

Like arthritis, menopause is associated with aging but can show up in young people as well. Since you may not realize this is possible, you may not be connecting the dots between potential gynecological issues and lack of sleep.

"Women are twice as likely to suffer from insomnia than men, according to the National Sleep Foundation, and their sleepless nights have been linked with hormonal changes —especially during menopause, when hormone levels are erratic," Dr. Kent Smith, founding director of Sleep Dallas, tells Bustle. Making sure you regularly see an OB/GYN, and always tell your doctors about changes to your health, can help you stay on top of these potential issues.

Tossing and turning doesn't have to be something that you ignore. Health issues like restless leg syndrome could be seriously impacting your ability to fall and stay asleep.

"Approximately one in 10 adult Americans suffer from Restless Leg Syndrome, according to the National Sleep Foundation," Dr. Smith says. "This sleep-related movement disorder causes overwhelming and often unpleasant urges to move the legs while at rest, often making it difficult for sufferers to drift off to sleep." If you find it particularly hard to lie still at night, it may be best to get in touch with a doctor.

While sleep apnea is known to cause disruptions during sleep, it can cause difficulties during the process of falling asleep as well. And since sleep apnea can be difficult to diagnose, you might not connect the dots on this sleep disorder immediately.

"Sleep apnea, a condition in which a person ceases to breathe multiple times per hour when they sleep, can inhibit a person’s ability to fall asleep," Dr. Smith says. "The brain detects that it is receiving less oxygen during sleep, so, in a life-preserving attempt, it actively prevents the sufferer from falling asleep." If you have difficulty falling asleep, plus other signs of sleep apnea, then it's important to see a sleep specialist and seek treatment.

Sometimes, the root cause of your difficulty falling asleep can be hard to pinpoint but relatively straightforward to treat. One of the examples of this is vitamin deficiency.

"Several common vitamin deficiencies can lead to sleep disturbance," Arielle Levitan, M.D., co-founder of Vous Vitamin LLC, tells Bustle. "[...] Determining which vitamins to take and in which safe and proper doses is important." Particular deficiencies like magnesium and iron can cause difficulty falling asleep, Levitan says. To find out if this is a problem, the first step is to speak with your doctor and potentially have them perform blood tests to check for deficiencies.

In order to protect your physical and mental health, it's important not to normalize your difficulty falling asleep. Taking note of why you may be struggling to fall asleep within 20 minutes or so, and how you feel the next day, may provide you some of the data you need to discuss this issue with your doctor — and find a treatment that works for you.