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.