For centuries, valerian root (Valeriana officinalis) has been the go-to herb to address anxiety and insomnia, often in combination with skullcap and/or passionflower. Also known as setwall and all-heal (as many herbs are), this member of the honeysuckle family was well known to the ancient Greeks and Romans. It was commonly grown in monastery gardens in England, where the 17th century herbalist Nicholas Culpeper praised the many virtues of valerian when he wrote, “the root boiled with liquorice, raisons and aniseed is good for those troubled with cough. Also, it is of special value against the plague, the decoction thereof being drunk and the root smelled. The green herb being bruised and applied to the head taketh away pain and pricking thereof." In addition to its mild sedative action, valerian root has been used in traditional medicine for anxiety, migraines, general pain and convulsions.
For many years, scientists have studied the impact of valerian root compounds on cortical excitability in terms of modulating gamma-aminobutyric acid (GABA), specifically GABA-A and GABA-B receptors. The system of inter-neuronal communication is made possible with each neuron being assigned to a specific task and its ability to carry out that task. This is how the brain learns, forms memories, performs abstract thinking and responds emotionally to stimuli. These neural connections are not fixed and can be altered. Impaired communication can lead to a variety of neurological disorders, including epilepsy, amyotrophic lateral sclerosis (ALS), stroke, migraine, Parkinson’s disease and dementia.
Using transcranial magnetic stimulation (TMS), scientists can measure cortical excitability non-invasively by observing muscle activity recorded on electromyography (EMG). In a recent randomized, double-blind, placebo-controlled and crossover study, scientists examined the effects of 900 mg of Valerian officinalis extract ( 0.8% valerenic acid) on cortical excitability measured with TMS in 15 healthy volunteers. The researchers found that valerian root significantly decreases intracortical facilitation, with activity returning to baseline level six hours after dosing.
Badawy R, Loetscher T, Macdonell R, et al. "Cortical excitability and neurology: insights into the pathophysiology."Funct Neurol. 2012 Jul-Sep; 27(3): 131–145.