We've all been there ”” you booze a little too hard one night and wake up feeling out of whack the next day. This feeling of grogginess isn't just an effect of your hangover, though ”” it's due to your restless night of alcohol-induced sleep.

Anybody who has ever imbibed in too much vino or tequila knows that booze makes you fall asleep fast. Studies show that drinking causes you to enter deep sleep about 8 minutes sooner than normal.

Falling asleep this quickly doesn't mean you'll get 8 extra minutes of beauty sleep, though, as all of the negative effects of your drunken sleep will catch up to you in the second half of your sleep cycle. Alcohol makes it easier to fall asleep, but only because you're falling into a far less restful sleep than your body actually needs. 

When there's alcohol in your system, your body forgets to calm down the nervous system, which means that your heart rate remains elevated by 13 beats. Since your nervous system doesn't have a chance to rest at night, you'll feel less rested when you wake up.

In a typical night, you will go through about five to seven cycles of REM sleep, and your body needs these restorative REM cycles to process all of the stress and emotions from your day. Alcohol drastically cuts your REM sleep to just one or two cycles, which is why you often feel foggy and exhausted the day after a crazy night out. 

Even if you're not typically a snorer, a sleeptalker or even a sleepwalker, your boozy sleep can make you a nightmare to share a bed with. According to sleep specialist Michael Breus, alcohol increases your chances of sleepwalking, snoring and sleeptalking.

When you knock back a few drinks at your co-worker's birthday party, you're going to spend the night tossing and turning. Sure, you fall asleep fast when you're a bit drunk, but you'll likely find yourself waking up between 4 and 6 in the morning. This early morning restlessness occurs because your sympathetic nervous system (which was never shut down properly) fires up, according to Stanford University's Seiji Nishino, Ph.D.

After a not-so-restful sleep, the only thing you want to do is continue sleeping, but your body isn't having it. Once your sympathetic nervous system kicks in, it's nearly impossible to fall back asleep. So you wake up earlier than you'd like, but even more disappointingly, you wake up feeling groggy and probably a bit hungover.

Now, we're not saying you should give up alcohol completely. By all means, party on, but now at least you know why you can never seem to get a good night sleep after downing a few beers.