Today is allegedly ‘Blue Monday’, the gloomiest day of the year. Workers are being asked to dress in flamboyant colours in their offices to help them overcome the January blues. Mental Health Research UK says we should let loose with bright patterns and fabrics on 'Blue Monday', renamed 'Blooming Monday' by the campaigners - a spot of ‘wearapy’ as some therapists call it. The idea is to lift our collective mood and raise awareness of depression and seasonal affective disorder (SAD), as well as raise money to combat mental health issues. SAD is a psychological dysfunction that stems from a shortage of natural daylight in winter months. This Monday is not long after the shortest, darkest day of the year and comes after Christmas festivities have ended: it is a long time until spring, and typically people feel rather low on what is often a cold, grey day, the campaigners say. The common work culture, especially in London where lunch breaks are frowned upon, may be contributing to the increasing numbers of those suffering from SAD. Certainly nutritionists suggest as many as half of us may be deficient in Vitamin D. This particularly matters if you suffer from low mood. Research shows those susceptible to depression record especially low vitamin D levels, explaining the tendency of those in northern climes to be more likely to succumb to the Black Dog than those in sunnier parts of the world. Diet can help and we all know it makes more sense to get our vitamins from food rather than supplements. Oily fish, eggs and fortified breakfast cereal all contain vitamin D. But the amounts they supply don’t come close to the power of sunlight, says my doctor.  The NHS recommends a daily dose of between 0.01 and 0.025mg. Here’s a thought: why not wash down your daily tablet with a warming mug of hot chocolate – one of the cosy benefits of winter. If the chocolate is dark enough, it can help boost serotonin levels too. And grab every last ray of sunshine you can: that’s the doctor’s orders. There’s something to be said too for wearing bright colours. Keats always used to put on his finest clothes before he wrote a poem and I remember a nattily dressed therapist telling me that she always took trouble with her outfits. ‘People’s outward appearance reflects their inner mood. But it is partly a case of chicken and egg: if you wear pretty, bright clothes on the outside, it may help you feel cheerier on the inside’. It isn’t necessarily as straightforward as slipping on something bright: research has shown that different colours can produce different mental states, both in us and in those around us. Blue clothing inspires calmness and tranquility, whilst a flash of green projects a refreshed state of mind. Yellow can be good for encouraging warmth and openness in others. And an orange exercise top might give just the extra boost you need to motivate you for a gym session or dance class. Another tool that never fails to improve my mood is, perhaps surprisingly, poetry. All this talk of bright colours is bringing to mind the much-loved poem by Jenny Joseph, ‘Warning’, which has inspired a whole tribe of purple-wearing, red-hat-brandishing women here and across the Atlantic with its hilarious opening lines: ‘When I am an old woman I shall wear purple/With a red hat which doesn’t go, and doesn’t suit me’. Humour is, of course, another brilliant counter to the ravages of low mood. When I am an old woman I shall wear purple With a red hat which doesn't go, and doesn't suit me. And I shall spend my pension on brandy and summer gloves And satin sandals, and say we've no money for butter. I shall sit down on the pavement when I'm tired And gobble up samples in shops and press alarm bells   And run my stick along the public railings And make up for the sobriety of my youth.   I shall go out in my slippers in the rain And pick flowers in other people's gardens   And learn to spit.   You can wear terrible shirts and grow more fat And eat three pounds of sausages at a go Or only bread and pickle for a week And hoard pens and pencils and beermats and things in boxes.   But now we must have clothes that keep us dry And pay our rent and not swear in the street And set a good example for the children. We must have friends to dinner and read the papers.   But maybe I ought to practice a little now? So people who know me are not too shocked and surprised When suddenly I am old, and start to wear purple.   This poem wonderfully articulates the fact that what we wear is so much more than a functional cover-up: it is a state of mind.