Research from the University of Oregon claims to prove that attaining a state of "restful alertness" for 20 minutes a day over a period of just five days can physically reduce anxiety and lower levels of the stress hormone cortisol.

The millions of people worldwide who practise meditation in its myriad forms may well allow themselves a wry smile at receiving the empirical blandishments of modern science. For theirs is a tradition that dates back nearly 3,000 years.

Not that anyone is certain exactly when it emerged, although most agree that the first meditators could be found sitting cross-legged among the Hindu tribes of the Indus valley shortly after Egyptian slaves had put the finishing touches to the Pyramids.

"There are some in India who say meditation was knowledge revealed to man from the beginning of creation. Then there is the historical account dating back to the 8th century BC, where you have a tradition of people involved in asceticism carrying out very early forms of yoga," he says.

At this stage in history, meditation was the pursuit of the upper classes – the aristocrats and warrior leaders – who would retreat to the mountains and forests of India to practise their new-found skills.

"They were trying to achieve transcendence, liberation and freedom. As Hindus they believed in karma – that everything you do sticks to you. Their main concern was to free themselves from this bondage."

A typical aristocrat of this time would have been one Siddhartha Gautama. The son of a king living in the Nepalese city of Kapilavastu around 600BC, the young prince grew up inoculated from realities of life – old age, sickness and death – realities that only became apparent when he was released from the confines of his palace and into the city.

According to Buddhist texts, so shocked was Siddhartha by the questions thrown up by his encounter with ordinary people that he embarked on a bout of ascetic living, surviving on as little as a single nut or leaf a day.

He collapsed and nearly drowned in a river before settling instead on a course of meditation, eventually achieving a state of enlightenment while contemplating under a pipal tree, known as the Bodhi tree, for 49 days. So Buddhism was born.

The Buddha spent the rest of his life travelling India and Nepal espousing his four noble truths and his eightfold noble path. His teachings formed the basis of Buddhist sects that spread across Asia. Though each retained a different emphasis, at their core remained the principle of meditation.

Meanwhile, back in India, there had emerged a new tradition alongside the Vedic system, which was based on the oldest and holiest of Hindu scriptures. Today Tantrism, as it became known, is an accepted prefix to the word sex, although Pomeda argues that this is unfair.

"[Tantrism] is misunderstood in the West, where it is associated with sex. But there are many thousands of tantric approaches. Instead of focusing on the solitary and the ascetic, they are about positively engaging with the world. Experiences on a deep level – love, beauty and joy – are used as a basis for meditation."

It is thought that yoga has been practised in India since 3000BC – at least according to those experts who believe early seals belonging to the ancient civilisation that grew up in the Indus valley depict the first seated meditating figure.

But it was not until the 12th century that the spine-stretching postures familiar in modern yoga were added. Before that, yoga was just about sitting and meditating.

The emphasis on physical contortion as a route to the purification of the mind was not formalised until the 15th century, when Yogi Swatmarama laid out the principles of hatha yoga, with its emphasis on asana – body postures – and pranayama – breathing.

These developments had little impact in the West until the arrival of colonists in India, when Europeans became seduced by the traditions of the East. At first yoga was studied as something exotic and strange, but then the theosophists attempted to synthesise their new-found knowledge with the Cartesian tradition of home, and to square it with the rationalism of the rapidly industrialising West.

The theosophists' doctrines represented a radical departure from the teachings of the mainstream Christian churches of the day. Founded by the colourful Russian émigré Helena Blavatsky in New York in 1875, and later moved to India, the Theosophical Society laid the foundation for what we now call the New Age, with its diverse and at times controversial beliefs.

This New Age was undoubtedly the forerunner of what many Westerners believe today. "In the 19th century we saw a specific quest for self realisation, and meditation was seen as a way of enhancing social function," says Dr Angelika Malinar, an expert in Hindu religions from the School of Oriental and African Studies in London.

"In the 19th century, meditation became part of stress-reduction programmes. It blended in well with people's concerns at the time – solving their psychological problems and mirroring individuals' quest for answers," she says.

As links between East and West grew, and travel became increasingly easy, Asian traditions grew in popularity. Eastern ideas were also being exported – the Chinese invasion of Tibet resulted in a mass exodus of Tibetan Buddhist priests, first to India and then to the West. The meditation master Chogyam Trungpa was one who took flight. He fled the Chinese army on foot, arriving in England in 1963 where he founded Britain's first Tibetan Buddhist monastery and counted among his meditation pupils a young David Bowie. Trungpa established the Shambhala movement – named after a mystical kingdom in the Himalayas – and founded the popular London Shambhala Meditation Centre in Clapham. Unfortunately for his followers, Trungpa's years of alcohol abuse finally caught up with him, and he died in Nova Scotia in 1987.

Meanwhile, on the other side of North America, the teachings of Shunryu Suzuki, a Japanese priest, had seen Zen Buddhism spread across California, at first to a beatnik audience but eventually into mainstream culture. But the most famous teacher of them all was the Maharishi Mahesh Yogi, who took his Transcendental Meditation world tour on the road in 1958 and set in train a spiritual movement that at the height of its fame was to sweep up some of the most famous people in the world, among them The Beatles, Mike Love of The Beach Boys, Donovan, Mia Farrow and later the comedian Andy Kaufman.

Despite its huge global following, even those who have studied and practised forms of meditation for decades admit that it is not a panacea.

A spokesman for the London Shambhala Meditation Centre says: "All we are offering here is a way of relating to your mind. Most people who try it out find it works very well indeed. But there is no ideal, it is a constant practice. There is no goal of reaching a Nirvana where you are like a cabbage and have no bad thoughts. They still come but you learn to observe them."

According to Carlos Pomeda, the truth can be scary: "Meditation is not a quick fix. It is not a comfortable place inside to hide away from yourself – in meditation you are confronting yourself."

How to meditate

Meditation has been around for possibly 5,000 years and is practised by billions of followers of all global religions – so there's no right or wrong way to do it. But at their core, all forms of meditation involve a state of concentrated attention, where the individual must turn thought inward and focus his or her mind on a single point of reference.

When sitting silently and comfortably, the meditator may find that their thoughts come thick and fast. Resistance is not only difficult, but often futile. Most practitioners will allow these feelings, fantasies and emotions to fade in and out, observing them as they come but each time returning to the central task of breathing, chanting or visualising a given object, although the "anchor" can also involve an exercise.

In the Buddhist tradition, the purpose of meditation is to realise the true nature of reality – enlightenment, in which the self is exposed as a false construct. Other religions, including Hinduism and Christianity, employ meditation as a means of exploring the truth of a higher power, or of achieving a feeling of closeness to a deity.

Meditation can be practised alone or in a group. It can be done once a week or every day, and a session can last for anything between 20 minutes and several hours. In India, some mystics meditate for years at a time. According to a recent study, the process of meditation contains five components – relaxation; concentration; an altered state of awareness; suspension of logical thought processes; and the maintenance of a self-observing attitude.

What the devotees say

George Harrison

"Meditation helps you find fulfilment in life, helps you to live life to the full."

David Lynch

"When I started meditating I had a real anger in me, and I would take this anger out on my first wife. Two weeks after I started meditating, this anger lifted."

Sting

"Yoga introduced me to a style of meditation. The only meditation I would have done before would be in the writing of songs."

Voltaire

"Meditation is the dissolution of thoughts in eternal awareness or pure consciousness without objectification, knowing without thinking, merging finitude in infinity."

Dalai Lama

"Sleep is the best meditation."

Mariel Hemingway

"Basically, I came to yoga and meditation so I could undo some of my past, and I believe that you can do that."

Tina Turner

"I am a practising Buddhist. In Buddhism there are words you can say... as you say the words with rhythm, the conscious tells the subconscious."