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Valerian (Valeriana officialis) is a common garden plant with pink or white flowers that is related to catnip and mint. Although the flowers smell sweet, valerian root smells unpleasant. However, valerian is known for its calming effects.
Valerian root tea is a common use, though it is also ground up and taken as a supplement, or as an extract in water. Either way, valerian has been used as a part of traditional European and Mediterranean medicine for thousands of years, including ancient Greece and Rome. 
Valerian root is used like a mild sedative to calm anxiety, reduce the feeling of stress, and to help the mind settle down before sleep. Valerian also may help with some forms of pain.
The feelings of calmness are difficult to test, however. The scientific evidence for using valerian root for anxiety and insomnia is shaky, and the results of small studies are mixed. Still, with its long history of use and lack of side effects, many people have found Valerian to be useful in reducing their anxiety or helping them sleep. 
Benefits and Effects
Most of the benefits of valerian root come from its sedative powers, which calm both the body and the mind.
Valerian root for insomnia is a common use of this herb.
Valerian calms down the mind and causes drowsiness, making it easier for people to fall asleep. Valerian also keeps the mind calm so that people stay asleep, waking up less often during the night. This leads to a more restful sleep and more energy during the day, which in turn improves mood. Using valerian root for sleep problems that come from other sources, such as menopause, appears to be especially effective. [3, 4, 5, 6]
Some studies measuring the sleep patterns of people with insomnia did not find any change in measured sleep patterns, though the people felt that they were sleeping better.  This study was small, however, and the emotional root of insomnia – which valerian may be helping with – is difficult to measure. [8, 9, 10]
Because of its calming effects, valerian root for anxiety is another common use for this herb.
By increasing GABA levels in the brain, valerian root may help to turn down the dial on your nervous system. This helps reign in feelings of fear and worry, and tones down the compulsive and ruminating behaviors that make up a large part of clinical anxiety.  Decreased fatigue from easier and better-quality sleep (aided by valerian root) can also give you better control over your anxiety and overall better moods.
Because anxiety is complicated, using valerian for anxiety should not be done on its own. Staving off the sources of your anxiety through changes to your lifestyle or through professional help may be more effective than valerian for anxiety alone.
Valerian root extract has been used to treat pain with some success. Valerian appears to be particularly effective for menstruation-related pain, possibly because it helps the muscles of the cervix, the cause of the cramps, to relax. [11, 12]
Valerian root extract may help reduce the intensity of the uncomfortable sensations known as “hot flashes,” as well as the sleep problems that sometimes come with menopause. [13, 14, 15]
Valerian root extract targets the same receptors in the brain as benzodiazepine, and has similar, milder effects. This makes valerian a good replacement substance to help wean people off of benzodiazepines and prevent unpleasant withdrawal symptoms. 
There is some evidence that valerian root extract may help the brain work better and regenerate from damage. The stress-reducing effect of valerian may be a part of this, too, as it reduces the levels of cortisol – a hormone associated with stress – in the bloodstream, which limits the ability of neurons to heal and regenerate. 
How Valerian Root Works
Valerian root contains a high amount of valerinic acid, which affects a neurotransmitter called GABA. Valerian root’s effects stem, mainly, from this action on GABA. 
GABA reduces the activity of the nervous system, helping to hold the brain back from being too active and is involved with how strongly we feel anxiety, fear, and feelings of unease. The more GABA we have, or the more efficiently our brain uses it, the less active our neurons are — and the calmer we feel. Drugs and supplements that affect GABA also reduce feelings of anxiety and fear.
Valerinic acid not only boosts the levels of GABA in the brain, it also prevents GABA from being broken down by the body. This keeps the GABA levels high for longer, creating a sedating or calming effect. 
Valerian may also influence glutamate receptors (which are involved with energy use in nerve cells), adenosine (which the body uses to regulate blood pressure) and 5-HT (also known as serotonin) receptors.  Though these other mechanisms are not fully understood, they may add to the sedative and calming effects of valerian. [20, 21, 22, 23, 24]
The standard valerian root dosage is about 450mg before bed, or 2-3 times daily doses of 300mg taken with meals. Higher dosages have more intense effects, but because of the potential drowsiness, you should start off low and see how it affects you. 
Is valerian root safe? Generally, yes. Valerian does not usually cause serious, life-threatening problems, even at high doses.  It does, however, have some Valerian root can lead to drowsiness even when taken during the daytime, and a valerian root overdose can lead to a state of mind that resembles drunkenness. Headaches, upset stomachs, lowered alertness, and difficulties in thinking and concentration are also possible side effects of valerian root.
It is important to keep in mind that the nervous system is delicate, and some people react strangely to herbal supplements. In some cases, valerian root can actually cause excitability and insomnia, vivid and un-restful dreams, and anxiety symptoms.
If you determine that valerian is not right for you, or if you plan on stopping your use of valerian root, you should reduce your dose over a week or two to avoid withdrawal symptoms.
Valerian root drug interactions
Valerian root interacts with alcohol, benzodiazepine, Xanax, sodium oxidate, and other sedatives both because it affects GABA and because it affects the ability of the liver to break down medications.  Usually, this means that valerian root makes other drugs work “better,” making those drugs behave as if they were taken at a higher dose. This can lead to undesirable and sometimes severe side effects. 
Because it interacts with anesthetics and other drugs, you should stop taking valerian 1-2 weeks before any surgery, and make sure that your doctor and surgeons are aware that you are taking valerian root. 
Valerian and the liver
Because valerian affects liver function, you should not take valerian if you have liver disease. 
Can you take Valerian during pregnancy?
There is not enough information to know whether taking valerian root during pregnancy can harm developing infants. Although valerian root appears to be safe for use in children, expectant mothers should consider weaning themselves off of valerian root for the duration of the pregnancy while this is still unknown. 
Valerian and Melatonin
Valerian root can be used together with melatonin to help with falling asleep. Both cause drowsiness, so if you are using them together, you should do so before you go to bed. You should also avoid operating heavy machinery or any activity that requires alertness after use – just use it for sleep. When taken alone, the general consensus is that valerian and melatonin are equally effective sleep aids, depending on body type.
Valerian and St. John’s Wort
Valerian and St. John’s Wort work together to help ease depression. Valerian’s calming effect not only enhances the positive benefits of St. John’s Wort, but it’s effect on GABA makes St. John’s wort a more effective mood boost. Keep in mind, however, that you may get a larger effect from the St. Johns wort for a given dose, so you may need to lower your usual dose of the herb to prevent side effects.
Valerian and Lemon Balm
Valerian and lemon balm have been studied together and have been shown to have calming effects on the body. They don’t appear to interact with each other chemically – they each have a calming effect that builds on each other. However, the combination of valerian and lemon balm appears to be especially effective for treating disturbed sleep that comes with menopause.
Valerian and Hops
Valerian and hops have been studied together as sleep aids and are safe to use. It is unclear whether this combination is more calming than valerian alone, however. 
Valerian and Passionflower
Valerian and passionflower are often used together. They do not appear to enhance each other, but both have calming effects and few side effects that add up well.