‘More than anything you guard, protect your mind, for life flows from it,’ says Proverbs 24:3, in the Common English Bible (CEB). The Contemporary English Version (CEV), is more precise: ‘Carefully guard your thoughts because they are the source of true life.’ An experiment by a social psychologist with an interest in the psychology of ageing showed how changing the way they thought about themselves renewed the youthfulness of a group of men in their 80s, even straightening out arthritic fingers.

Mind-sets are formed by consistent thinking that embeds ‘circuits’ of neurones in our brains. They can be positive or negative. They are described by Christian cognitive neuroscientist, Dr Caroline Leaf in her book, ‘Who Switched Off my Brain’. She describes how these circuits are formed and work, and how to ‘detox your thought life and live a life of physical, mental, and emotional wholeness.’

Although we know about the ‘mind-body’ connection, I think very few of us really know how powerfully it works. It was demonstrated in a study by an eminent Harvard social psychologist that had such startling results there was talk of making a film about it.

The study was conducted by Harvard’s Dr Ellen Langer, Ph.D., a social psychologist with an interest in the psychology of ageing, in particular on how our thoughts influence our bodies. One of her pressing questions was, ‘could we change our physical health by changing our minds?’ (If you’ve read my book, ‘ What's Age Got To Do With It’ you’ll read more detail about the study.)

It involved Dr Langer and her team taking groups of men in their 80s on a week-long retreat in a house that had been retrofitted and taken back in every way to 1955. Every item in the house belonged to that period of time. All the men were interviewed beforehand and took baseline physical and psychological tests. They were thoroughly briefed and prepared.

Those in the ‘experimental group’ were to live in the house as though they were living in 1959. They were not to bring any books, newspapers, or family pictures that were older than 1959. They were to go back in time, to turn their minds back and live in that year, not discussing anything after 1959. The team carefully studied what life was like in 1959 – the politics and social issues, the TV shows – everything they would have encountered in that year that would effectively take participants back to it. (It was a time when an IBM computer filled a whole room, and panty hose had just been introduced.) Researchers and participants met daily, and discussed events that were ‘then’ happening and watched films of the era.

The people in the control group came separately another week, just to enjoy the week and reminisce about 1959.

After each retreat, the team evaluated the participants and found that the experimental group came out of the experience with several physical improvements. Their hearing and their memory, even the strength of their grip significantly improved. Fingers lengthened in the experimental group as their arthritis diminished and they were able to move them with greater manual dexterity. There were improvements in height, weight, gait, posture, and scores in intelligence tests. On many measures the participants got measurably younger. In a short, intensive time, they had changed the way they thought about themselves and what they could do.

Finally, independent observers who were unaware of the experiment were asked to examine the photographs taken before, and after the week’s retreat. ‘Those objective observers judged that all those experimental participants looked noticeably younger at the end of the study.’

Dr Langer said, ‘Over time I have come to believe less and less that biology is destiny. t is not primarily our physical selves that limit us, but rather our mind-sets about our physical limits… We must ask ourselves if any of the limits we perceive as real do exist.’

The Proverbs were written thousands of years ago, by Israel’s King Solomon, ‘the wisest man who ever lived,’ says one commentary. Guarding our thoughts means choosing which ones to dwell on and which to reject. And Philippians 4:8 tells us how to do it: ‘Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things.’