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.

If you often feel a bit down or even truly depressed, you are almost certainly suffering from a deficiency of serotonin — the “Happiness Hormone”.

A basket of fruit with tryptophan in mind

Now a new ebook that tackles this problem in a Sideways manner is available by download. Caroline Longmore, a French doctor has created a programme for everyone, based on a natural diet.

Serotonin is derived from the essential amino acid tryptophan, which the body cannot make itself.

So for many of us, unless we take enough tryptophan through our diets, we may suffer a deficiency.

… The best way is through diet: eat foods rich in trypotophan and avoid sugar and processed carbohyrates which artificially raise blood-sugar levels, leaving you feeling temorarily better before even wilder mood swings. … you will also need enough vitamins B3 and B6, magnesium and zinc.

Typical foods recommended are, bananas, turkey, spinach, beans and seeds, cottage cheese, plums, lobster and pineapple.

You can download The Serotonin Secret, By Dr. Caroline Longmore and Katrin Hempel as an ebook, from www.galennaturopathic.com for £5.95, or dollar equivalent.