Malcolm Myatt, 68, had a stroke. It affected the frontal lobe of his brain, which is the part of the brain that governs emotions. As a result, he's lost the ability to feel sad. Experts say it is not uncommon for strokes to cause psychological, emotional, and behavioral changes.

The retired lorry driver said, "I am never depressed. Being sad wouldn't help anything anyway. I would definitely rather be happy all the time than the other way round. It's an advantage really."

According to The Stroke Association, many of the psychological changes that occur after a stroke are down to the physical damage of the brain and depend upon which part of the brain has been affected, as well as the extent of the damage,