You're lying in bed, your mind is racing, and you can't seem to drift off to sleep despite feeling tired. Most people blame this scenario on stress, nervousness, or anxiety, but there are several more likely factors keeping you awake. Here are five lesser-known causes of sleeplessness:

1. Alcohol

Alcohol is a sedative and may initially help you fall asleep, but a nightcap does more harm than good. It interferes with your natural sleep cycle and blocks the most important stages of sleep. You are also likely to wake up in the middle of the night after the alcohol wears off, and you will probably not feel refreshed in the morning.

2. Excessive Weekend Sleep

Sleeping in until noon on Saturday and Sunday might seem like a good idea, but the excess sleep can actually cause even more sleeplessness in the long run. Frequently changing your sleep schedule forces your body's biological clock to make constant adjustments, thereby affecting your quality of sleep during the week and weekend. Stick to a consistent sleep schedule seven days a week for best bedtime results.

3. Pets

Disruptions during the night take on many forms: pets in the bed, for example, can be a major source of trouble. Animals have a different biological clock than humans and may wake up in the middle of the night, walk around, and make noise. Most sleep experts recommend keeping pets out of the bedroom, or, at the very least, off the bed.

4. Your Late Afternoon Nap

Although occasional napping can be an effective way to catch up on lost sleep, too much sleep during the day can make it impossible to fall asleep at night. Avoid napping after 3 p.m. and set your alarm for one hour; any longer will cause daytime drowsiness and keep you up well into the night.

5. Medicine

If you are taking medication for any health conditions, check with your doctor to see if it could be interfering with your sleep. Many common drugs and some supplements can cause sleeplessness, including decongestants, steroids, and pain relievers. Certain heart and blood pressure medications can also interfere with sleep.