Scientists from the University of Michigan may have the answer - and it's not good news for pessimists. Whether you're an optimist or a pessimist may in your genes, they say. Why? Because they've discovered optimism (and therefore also pessimism) is directly related to levels of a molecule in your brain called neuropeptide Y (NPY).
So if you have low levels of NPY, you may be more likely to have depression than someone with high NPY levels. You may also be more prone to being negative and less likely to cope well with stress.
Published in the journal Archives of General Psychiatry the study describes tests carried out by the scientists. After having their NPY levels measured, a group of volunteers had their brains scanned while being shown neutral, negative and positive words.
Those with low levels of NPY showed increased activity in part of their brains called the prefrontal cortex - which processes emotion - while viewing the negative words. Those with higher NPY levels showed less brain activity in response to the negative words.
A second test involved inducing mild pain in the volunteers, and again those with NPY rated their feelings as more negative than those with higher NPY levels.
The study's findings don't, however, offer any advice for pessimists on how to be more positive.
What makes you smile when you're feeling gloomy?