Image caption Not everyone is cheered by spring

While the arrival of spring heralds a new lease of life and energy for most people, for those suffering from depression the effect can be drastically different.

Harvard psychiatrist John Sharp has done extensive research into the effects that the changing seasons have on our mental health and emotional well-being.

In his book, The Emotional Calendar, Sharp outlines how physical, psychological and socio-cultural factors influence the way we feel.

"Most people do feel an increase in exuberance, energy, optimism, excitement, maybe a restlessness and sleeplessness that can come from what the Americans call spring fever," he told the BBC World Service's Health Check programme.

The three realms

"We are exquisitely sensitive to the effect of physical influences on our mood and behaviour."

Dr Sharp breaks the effect of seasons into three big "realms".

The first is the physical realm - factors like light and temperature. Extra hours of sunlight and rising temperatures can increase the levels of serotonin and dopamine in the body - the chemicals responsible for feelings of well-being.

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The second realm features cultural events, such as festivals and summer holidays, that give people a positive outlook.

The third is event anniversaries. Whether it is something positive, such as a great achievement, or a negative event, like death and loss, seasonal cues trigger our senses and can cause us to relive these moments year after year.

For most people the first two factors conspire to make us feel more positive in springtime. But as Dr Sharp points out, for those who suffer from depression, spring can have the opposite effect.

"At the same time as most of us are rolling up our sleeves and spending more time outdoors, others struggle with trying to get into that kind of mode, and counter-intuitively, they feel worse."

It is not surprising, then, that in the UK suicide rates are at their highest in spring, peaking in April and May.

"If you're not being carried along with the natural energy of the season it can be really hard," says Dr Sharp.

Negative mood

Nicolas Werner, a mental health worker from Hove in East Sussex, agrees.

He was diagnosed with depression in 2001 and subsequently with bipolar disorder towards the end of last year.

Image caption Charities say there is a dearth of information on depression

"Many people look at spring as new beginnings, something positive. This is a sharp contrast with how people with depression feel and exacerbates the condition.

"Daffodils are out, the sun is shining and people are still feeling terrible."

It is something he feels personally.

"In March when I know we're putting the clocks forward I'm not looking forward to that, so that gives me a negative sort of mindset," he says.

"It is like the winter was an eiderdown or a duvet to hide underneath, but in the long summer hours or daylight hours I felt more exposed."

As the low mood sets in he can feel irritable, has trouble concentrating and has racing, suicidal thoughts. He also loses interest in the things he usually enjoys.

"I'm a book-worm. When I'm feeling ill I lose interest in reading," he says.

This year he was absent from work with illness for almost a month between March and April.

What Werner suffers from is known as reverse Sad (Seasonal Affective Disorder).

Emer O'Neill, of charity Depression Alliance, acknowledges the seriousness of the condition.

She says: "Reverse Sad is rare but this has a lot to do with the fact that so little is written about it. It is not talked about so there are potentially many people out there who have the condition and have not been diagnosed.

Seasonal triggers

"There is a dearth of information on depression and this needs to be addressed."

Books like Dr Sharp's, then, can be an important tool in helping sufferers to see their altering moods in a new light.

And for Werner a similar approach has helped him to deal with his cyclical depression.

Since he was diagnosed with bipolar disorder last year Werner has been observing his own behaviour patterns. He has linked his low mood to an attempt he made to take his own life.

His own observations correlate directly with Sharp's theory that it is not just the physical factors of seasonality but psychological and social factors, too, that affect the way we feel.

This new understanding can help sufferers like Werner. By being aware of certain seasonal triggers he can learn to manage his depression.

"I think I've gotten to the root of it," he says. "So I hope this summer will be different."

But thousands of people who suffer from depression remain undiagonsed in the UK.

"We all have to be careful that the people around us who seem unduly glum are getting support and talking to their doctor or their therapist and not feeling isolated and alone," Sharp affirms.