Occasionally you have a bad night’s sleep and you know exactly why: it was that after dinner espresso or your loud snoring partner. But many times you have no clue as to why that restless night turns you into a zombie the next day. Here are seven unusual (and surprising) reasons you’re not sleeping.

1. You’re Actually Afraid of the Dark

Fear of the dark isn’t just for little kids, many adults feel anxious and uncomfortable once the lights go out. Sensitive people are especially susceptible, often startled by noises and strange shadows. Try sleeping with a night-light or use a dimmer switch and see if that makes a difference.

Fear of the dark isn’t just for little kids, many adults feel anxious and uncomfortable once the lights go out.

2. Your Bedroom Is Too Hot or Too Cold

You might not realize it, but research indicates that there is an optimal sleeping temperature. It’s somewhere between 60 and 67 degrees Fahrenheit. Make sure your bedroom is in the zone.

3. Your Bedroom Is Too Quiet

Believe it or not, too little noise is almost as bad as too much! A too quiet bedroom could be your problem. If so, it’s easily remedied with a white noise machine.

4. You’re Overtired

You’re totally exhausted, so you should just crash and fall fast asleep, right? Not necessarily. Being exhausted or overtired isn’t the same as being sleepy. Unfortunately those stress hormones are still keeping you up. Try winding down first before your head hits the pillow.

5. You Slept in over the Weekend

Did you try to catch a few extra zzzz’s over the weekend? Although it sounds like a great idea, it can throw off your body’s biological clock—leaving you sleepless for the remainder of the week.

6. You Were on the Computer Before Bedtime

The bright electronic glow of that computer screen right before bed can also disrupt your sleep rhythm. The same goes for the entrancing glow of a television screen. Turn off these electronics about an hour before bedtime.

7. There’s a Full Moon

Don’t worry, you’re not destined to change into a werewolf, but a full moon can cause sleep disturbances, at least according to one study. You’re likely to experience less sleep overall, as well as less deep sleep. It will also take you about five extra minutes to reach dreamland.