Passion flower among many other supplements has been found to take the edge off the stresses and strains of modern life say U.S. scientists.
The team, from the Global Neuroscience Initiative Foundation, a mental health charity, scrutinised 24 studies into supplements commonly used to reduce stress.
Magnesium supplements ‘hold promise’ but need more research before they can be recommended to combat anxiety, say the researchers.
But passion flower supplements do seem to work, although some people who take them suffer side-effects such as dizziness, drowsiness and confusion.
Also effective are lysine and arginine, two of the building blocks of proteins.
Kava kava, a herbal supplement banned in the UK because of safety fears, was also deemed to work.
The findings are important because although anxiety is often dismissed as a minor irritation, in the long term it can raise the risk of heart attacks and strokes.
In the short term, symptoms can include headaches, stiff and sore muscles and uncontrollable trembling and sweating.
The researchers said: ‘Anxiety is characterised by a feeling of persistent worry that hinders an individual’s ability to relax.
‘Over the past several decades, complementary and alternative medications have increasingly become part of everyday treatment.
‘With the rising cost of prescription medications and their production of unwanted side-effects, patients are exploring herbal and other natural remedies for the management and treatment of psychological conditions.
‘Based on this systematic review, strong evidence exists for the use of herbal supplements containing extracts of passion flower or kava kava and combinations of lysine and arginine.’
But the team cautioned that not enough is known about the best amount to take.
Researcher Shaheen Lakhan said: ‘Herbal medicines hold an important place in the history of medicine, as most of our current remedies, and the majority of those to be discovered in the future, will contain phytochemicals – chemicals derived from plants.
‘Understanding the quantity needed and the potency of different ways of extracting and preparing the phytochemicals is vital to creating a standard measure of their effectiveness.’