Sleep disorders is a broad category encompassing of variety of conditions that affect sleep. Often, sleep disorders have environmental or behavioral causes: the result of stress or poor sleep hygiene. But this is not always the case: Restless Leg Syndrome is a neurological disorder, without links to any specific environmental or behavioral cause.

It's 3am. You've been lying awake for hours. Finally, sleep comes. Thoughts slowly drift off. Try to hold onto one and it flits away. Turn over once more. Snuggle close. Fall into the blissful unconsciousness of sleep.

But then. There's that feeling. At first you're only dimly aware of it; a slight tingling in your dream, perhaps. But it grows stronger. Burning and itching creep up and down your legs. Your legs might even start twitching. You might wake up. Your bedmate certainly will.

The itching gets so unbearable that you can think of nothing else. You vigorously rub you legs. You jump out of bed. You walk around the house, around the block. You have to do something, anything, to get it to stop. It subsides for a time, but as soon as you lie back down that creeping, that aching comes right back and you can't sleep.

Restless Leg Syndrome (RLS) is a painful disorder characterized by the overwhelming need to move your legs while sitting or lying down. A burning or itching sensation occurs during inactivity and is most severe at night. Symptoms are relieved by motion or pressure, but only temporarily. The exact cause of RLS is unknown, but there appears to be a genetic link. Dopamine and serotonin also appear to be a factor in causing RLS: medications that affect serotonin and dopamine can cause RLS.

RLS has several types of treatments: medication can help, as can stretching periodically or practicing yoga or Pilates. Additionally, consider picking an aisle seat during movies or on airplanes. That way, you're free to get up and walk around.

And, as always, if you have trouble sleeping, if you're constantly tired, talk to your doctor. Sleep diary can also help. Keep track of how well you slept each night and what you did during the day: how much caffeine you drank, what you ate. Things like that. It can provide a wealth of information about your sleeping patterns and behaviors.