As the nights draw in, millions of us feel gloom setting in. But there are ways to lift your mood in the colder months, says Rebecca Armstrong

Use a light box

The summer of 2007 has already gone down in history as the wettest since records began. If months of grey skies, rained-off barbecues and ruined trips to the seaside weren't depressing enough, this lack of sun could also be having an effect on the happiness of millions of us. Whether you are a signed up sufferer of seasonal affective disorder – along with more than a million other people in the UK – or simply feel your mood dip as the nights get darker, the consequences of a lack of sun can leave people lethargic, depressed, anxious and more likely to get colds and infections.

There are a number of theories about exactly what causes SAD but the common theme is that light triggers messages to a part of the brain called the hypothalamus. This controls sleep, mood and appetite so it's thought that the lack of sunlight in winter has an impact of how effectively it manages these functions.

However, there are a number of ways to combat SAD and one of the most effective is simple to use and can have results within three days. Exposure to bright light – phototherapy – helps 80 per cent of SAD sufferers, according to the mental health charity Mind. Ordinary light bulbs aren't strong enough, though, as the average domestic or office light only emits an intensity of 200-500 lux while the minimum dose necessary to treat SAD is 2,500 lux. The easiest way to get this kind of light is by investing in a light box – prices start from about £60 – and sitting in front of it for around one or two hours a day. Boots has seen sales of its range of light boxes soar by 147 per cent this year.

Get outdoors

In the depths of winter it's easy to stay indoors and shun any unnecessary trips outside, especially if the weather is foul and temperatures are freezing. However, leaving the house can have a huge effect on mood. According to NHS Direct, anyone who suffers from SAD or low moods associated with winter should try to get as much natural sunlight as possible. "Even a brief lunchtime walk can be beneficial," advises the site.

Research published earlier this year suggests that during winter, 90 per cent of British adults suffer from a shortage of vitamin D. The study's author, Dr Elia Hypponen, says that "a sensible outdoor lifestyle... will make adequate vitamin D." If it's impossible to leave the house or office during daylight hours, Mind recommends sitting near the windows in light-coloured rooms. According to a study by the University of Essex, being closer to nature increases well-being and even looking outside through a window, especially on to a view of nature, can have a significant effect on moods. Although the shorter winter days don't have the same light intensity that occurs in summer, if you suffer from SAD it's important to spend as much time in daylight as possible. But while being outside can help ease the symptoms, it's not a total cure – many farmers and outdoor workers suffer from the disorder despite spending their working hours in natural daylight, as Mind points out.

Take exercise

One way to keep on top of the winter blues is to exercise regularly. A 2001 study by the Duke University in North Carolina found that exercise is a more effective treatment for depression than antidepressants, with fewer relapses and a higher recovery rate. The reason why exercise has such a profound effect is that physical activity increases the amount of endorphins in the body and endorphins boost feelings of happiness. "I can't believe how obvious it is but people really need to get out and exercise," says Emer O'Neill, chief executive of the Depression Alliance. "But when you're feeling permanently tired, fed up and sluggish, being told to exercise is really irritating. It's a catch-22 situation, but if you can start exercising at the start of the season and just try and build in a regular routine it really helps."

If you're loath to jog in the dark or join a sports club, an exercise video, trip to the gym or a yoga class are extremely effective ways to improve energy levels and boost moods. In fact, any physical activity lasting between 20 and 60 minutes can help to improve psychological well-being, according to a recent report from the Mental Health Foundation.

Improve your diet

Comfort food tends to be the standard fare during winter, but craving carbohydrates is a symptom of SAD and although eating stodgy foods can be soothing in the short term, it can lead to lethargy and weight gain. "People often gain weight when suffering from SAD and putting on between 5 and 10kg is quite common," according to Dr Jonathan Johnston, a lecturer in neuroscience at the University of Surrey who specialises in seasonal biology. Nutritionist Patrick Holford recommends following a diet that keeps blood sugar levels even and provides plenty of omega-3 fats to keep your moods and your weight under control. "Avoid sugar and sugary snacks and try to reduce your intake of stimulants – tea, coffee, chocolate, alcohol and cigarettes," he says. "Increase nutrient-rich foods – fruit, vegetables and wheatgerm – and eat tuna, mackerel, herring or salmon three times a week." Holford also advises eating nuts and seeds – go for flax, hemp, pumpkin, sunflower and sesame. "It's also important to minimise your intake of fried and processed food and saturated fat," he says.

Consider antidepressants

In severe cases of SAD, some doctors may suggest taking serotonin re-uptake inhibitor antidepressants (SSRIs) during the winter months. "For some people it is useful to go on antidepressants – obviously after going along to see your GP," says O'Neill. "At the diagnosis stage it's important to recognise if the condition has happened before and if you always have symptoms of depression that start to kick in around this time of year. A low level of antidepressants can lift your mood and break the cycle." But combining treatments can be even more helpful than simply relying on prescription drugs. "Taking antidepressants while using a light box can be very effective. Just remember that when you go to your GP it's important not to think that antidepressants are the only way – there are lots of other treatments that work."

For those who don't want to take prescription pills, there are alternatives. "St John's Wort is known worldwide as an effective antidepressant – in Germany it's the most frequently prescribed antidepressant and out-prescribes drugs like Prozac," explains Jayney Goddard, the president of the Complementary Medicines Association. "There are new formulations that include passion flower, a herb that has anti-anxiety properties." Goddard has successfully used this mixture to treat a number of her patients. "The herbal approach is one of many ways to help deal with SAD," she says, "but from what I've seen it's very effective."

Take supplements

Another possibility that is beneficial to health as well as helping to lessen the blues is taking cod liver oil. "Taking cod liver oil every day can strengthen the immune system," explains GP Dr Sarah Jarvis. "You also get a healthy dose of vitamin D that can protect against depression." During the summer, people usually build up a store of vitamin D in their bodies but it will only last about 20 to 29 days. Once it has been used up, it's necessary to increase the store by taking supplements or getting some winter sun.

Try a talking cure

If you're feeling unhappy, it's important not to suffer in silence, says O'Neill. "We recommend talking about how you feel – be really clear with your GP and talk to your friends." Some SAD sufferers find Cognitive Behavioural Therapy can be helpful, she adds. "Your GP can refer you but there is usually a waiting list. Computerised CBT is an effective tool for people, especially those who recognise that they do feel down at this time of year. Once you buy it, you use it when the time is right for you."

Another alternative is group therapy. "Some people find support groups helpful," says O'Neill. "For most people, feeling like this isn't life-threatening but it's a very uncomfortable thing that you don't have to go through alone. There's help available and talking about how you're feeling can really make a difference."

Get some winter sun

People who live within 30 degrees of the equator seldom suffer from SAD, thanks to long hours of daylight and bright sunshine. Head further north or south, however, and SAD symptoms become more prevalent. An estimated 10 per cent of the population of northern Europe suffer mild SAD thanks to a combination of dark days and infrequent sunlight. "Some people have suggested that SAD is like a human form of hibernation – perhaps it's a vestigial link to animal behaviour," says Dr Johnston. It's hardly surprising that we're sluggish and sad in winter if our bodies would rather curl up for a three-month nap. So what can people dwelling in the dark north – or south – do? Booking a holiday in January or February not only gives you something to look forward to but can give you much-needed exposure to sun and light. Or if your funds are unlimited, says Dr Johnston, "moving to somewhere sunny for three months over the winter would be great for everyone!" Not an option? Stick to a daily walk, a blast of the light box and a healthy diet.