Rachel Kelly is the author of "Black Rainbow", a powerful and best-selling memoir on how she survived profound depression.

The book describes how poetry gave Rachel hope in the darkest of times, an idea which led to us working with her on a new project called Postcards of Hope. Here Rachel writes about how she first came to understand the full healing power of poetry.

Seventeen years ago I experienced my first bout of depression which was so painful that it seemed nothing could reach me. It was then that my mother and constant companion would sit by my bedside and repeat a line from Corinthians: ‘My grace is sufficient for thee: my strength is made perfect in weakness.’

These thirteen words helped reverse my negative thinking that nothing good could come from the illness. Instead, I would become stronger because of the ordeal. I often think of depression as like a trapdoor opening inside me: I would repeat the words my mother gave me endlessly, mantra-like, when I felt in danger of falling through. They were at the heart of my recovery.

Since that first depressive episode I have continued to battle with depression, but thanks to drugs and therapy and above all poetry, I am keeping the Black Dog on a tight leash. When very low, I am still only well enough to absorb one phrase, be it from the Bible, which of course is full of poetry, or elsewhere. Favourites include the last lines of Arthur Hugh Clough’s ‘Say Not the Struggle Naught Availeth’, also famously quoted by Winston Churchill in his wartime speeches.

In front the sun climbs slow; how slowly,

But westward, look, the land is bright’.

Another favourite is almost any line from Emily Dickinson’s ‘ “Hope” is the Thing with Feathers’ in which the poet compares hope to a bird. (Indeed there are many poems in which tiny birds are symbols of hope.) Hope is always there, even if it’s small and in your peripheral vision.

‘Hope’ is the thing with feathers –

That perches in the soul –

And sings the tune without the words-

And never stops – at all –

I began to discover that I was far from alone in finding poetry helpful in dark times. The novelist Daisy Goodwin has a ‘Poetry Doctor’ section on her website, while the philosopher Alain de Botton’s ‘The School of Life’ has recently begun courses in mindfulness and poetry. Meanhwhile, William Sieghart, founder of the Forward Poetry Prize writes ‘Poetry Prescriptions’ at various literary festivals with queues round the block.

Of course the healing power of words has a long history, dating back to primitive societies who made use of chants. By the first century AD, the Greek theologian Longinus wrote about how he believed in the powers of language to transform reality, to affect readers in deep and permanent ways, and to help them cope with the vagaries of their existence. Spool forward to the twentieth century and by 1969 the Association of Poetry Therapy was established in the USA.

Since I first discovered how helpful poetry could be, I’ve developed something of my own cottage industry in consolatory verse. Initially I swapped helpful poems with friends; now I am lucky enough to work with the Education Department at Wormwood Scrubs and several mental health charities, organising workshops which celebrate the healing power of poetry.

My proudest moment came recently when one of the inmates at the Scrubs told me he had stayed up all night with the anthology of poems I co-edited for Canongate, ‘If: A Treasury of Poems for Almost Every Possibility.’ A section at the back recommends specific poems to try and help those who need courage, for example. It has proven incredibly popular and that anthology is now in its fourth edition.

Just why is poetry so powerful? That's a question I'll try and address in my next blog.

By Rachel Kelly