Valerian root has been one of the best-known natural sleep aids at least since Roman times. The Romans called the raw herb phu, referring to its pungent odor. A large dose of valerian could knock you out in more than one sense of the term. If the smell didn't cause you to pass out, the tea would put you to sleep.  Despite its odor, valerian is one of the best known and most reliable herbs as natural sleep aids.
In modern times, valerian teas and valerian extracts (in capsules) are used both to induce sleep and to help their users stay asleep. They have been clinically tested, but because different clinical trials used very different doses of the extract (ranging from 225 to 1215 mg of extract and/or root), results vary. Some of the scientific studies looked at results of people's using a combination of valerian and lemon balm (melissa) extract..
How Does Valerian Work?
Laboratory studies with mice concluded that a component of the valerian root called valerenic acid changes the way receptors in the brain respond to a compound called GABA (gamma-aminobutyric acid). GABA activates inhibitory neurons in the brain. These neurons "turn off" the neural circuits that generate anxiety and insomnia.
Because benzodiazepine drugs such as Ativan and Valium also modulate GABA receptors in the brain, and these prescription drugs cause serious side effects, researchers took care to confirm that valerenic acid doesn't cause drowsiness or sleepwalking or loss of coordination of delayed reaction time. Even though the herb and the drug work on the same receptors in the brain, they don't cause the same side effects. 
The bottom line of at least 167 studies of valerian and sleep is that the herb helps relieve insomnia, and it doesn't cause side effects. Valerian is a product you can use safely and effectively by itself or in combination with lemon balm, hops, and/or passionflower to ease your nighttime sleep problems.
Other Uses of Valerian That Can Help Sleep
Valerian isn't just an insomnia treatment. It is a time-honored remedy for anxiety. It works by helping the brain conserve not just one but two neurotransmitters, serotonin and norepinephrine . Its action is similar to the prescription medication venlafaxine (Effexor), but without the side effects (especially flatulence). The herb has been successfully tested in a clinical trial as a remedy for anxiety at the dentist's office during tooth extraction , A combination of valerian, passionflower, and St. John's wort has been found to relieve test anxiety in children .
The combination of valerian and lemon balm is successfully used to treat insomnia caused by hot flashes in menopause. The herbs don't completely stop hot flashes, but they helped measurably and significantly in a clinical trial. 
Valerian used by itself relieves the pain of menstrual cramps .
A combination of valerian and lemon balm has been clinically tested for relief of sleep problems and other issues related to ADHD in children. A study sponsored by the German herbal products maker Dr. Willmar Schwabe Arzneimittel (full disclosure, one of our Steady Health writers has received a grant from them) parents of children with attention deficit hyperactivity disorder were given a daily dose of 640 mg of valerian root extract plus 320 mg of lemon balm extract reported that their children slept better. However, the researchers also noted that "The fraction of children having strong/very strong symptoms of poor ability to focus decreased from 75 percent to 14 percent, hyperactivity from 61 percent to 13 percent, and impulsiveness from 59 percent to 22 percent." [9[
There is a body of evidence that supports the use of valerian for treating restless legs syndrome . It's not as useful for restless legs syndrome as any of the prescription drugs or compression stockings, however .
How Do You Use Valerian?
It's always possible to brew up a valerian tea. You will have to guestimate how much of the active ingredients you are getting, but you should be able to tell what works for you. Use hot water, not boiling water, and use a tea pot (or cover your teacup with a saucer while the tea is brewing), so the active ingredients don't evaporate.
It's easier to take valerian in capsules. Any dose of 500 to 1200 mg of the extract form of the herb taken an hour before bedtime is adequate.
Is Valerian Safe?
Valerian is nontoxic and safe even in pregnancy . Laboratory testing has confirmed that valerian neither activates nor deactivates any of the liver enzymes the body uses to process common prescription drugs . This means that it is safe to use with the medications you have to take for other conditions, although it's always a good idea to let your doctor know about all the over the counter supplements and herbs you are taking.
Taking as much as 1600 mg of valerian extract in a single dose won't affect your driving skills . A Chinese species of valerian that is best known as zhizhuxiang (its botanical name is Valeriana jatamansi Jones) has been used for centuries for treating insomnia, and also for fatigue, bloating, and joint pain. You could take a huge dose of the herb and have no adverse effects--but always use as directed. 
There's not a lot than can go wrong with valerian. However, avoid the herb if you have been diagnosed with low sodium levels (hyponatremia), and avoid taking the herb with licorice (found in Chinese patent medicines) as a chronic insomnia treatment, for more than four weeks at a time.