If you have ever been diagnosed as suffering from depression, or suspect you may have a depressive illness, take heart.

Professor Jerome Wakefield of New York University believes sadness and depression are essential tools of evolution that prompt “sufferers” to become high achievers in life. He cites Winston Churchill, Beethoven, Abraham Lincoln and Isaac Newton as depressives who made good.

Wakefield says: “When you find something this deeply in us biologically, you presume it was selected because it had some advantage, otherwise we wouldn’t have been burdened with it. We’re fooling around with part of our biological makeup.”

He further believes that medical diagnoses of depression and its treatment with powerful drugs, like Prozac, is an unnecessary and dangerous fad. His book, The Loss of Sadness: How psychiatry transformed normal sorrow into depressive disorder states that sadness helps us learn from our mistakes. “I think one of the functions of intense negative emotions is to stop our normal functioning — to make us focus on something else for a while.”

So, if you are feeling down and are tempted to pursue the chemical route to “salvation”, consider that a deep part of yourself may be attempting to convey something to you.

At least try to find out what it is before heading for the doc’s surgery.

According to research at the University of California, people with a sunny disposition live on average seven and a half years longer than gloomy types.

Moreover, the risk of dying early from any disease is 55pc lower for optimists than for pessimists.

People with a pessimistic outlook will have higher levels of anxiety and an increased risk of developing Parkinson’s disease in later life.

Dr James Bower of the Mayo Clinic said, “What we have shown for the first time is that there’s a link between an anxious or pessimistic personality and the future development of Parkinson’s.”

The theory is that optimism increases the will to live and to participate in life. This may lower levels of the stress hormone cortisol.

Researchers at Carnegie Mellon University, Pittsburgh, also say that optimism boosts the immune system and protects from psychological stress.

Over a 30-year period, say the researchers, optimists had fewer disabilities and less chronic pain.

Can you develop an optimistic lifestyle? We will be writing about that soon.