Many people who feel depressed experience ‘negative rumination' (overthinking about negative things). But this overthinking about bad stuff could actually help us solve important, complex problems!
According to this theory, we might experience changes in our brain or body that stop us getting distracted, so we can focus on our stressful problems.
These changes include some familiar symptoms of depression – like low energy and no interest in things we used to enjoy.
If this theory is right, these periods of ‘negative rumination’ were evolved to last a short time, and once we solved a problem, we would start to feel better.
But modern life is very complicated! If people are trying to deal with overwhelming problems they can’t solve for a long period of time, they might get ‘stuck’ and feel depressed long-term.