Sometimes I can't sleep because a problem plays over and over in my mind. Does this happen to you?

Psychologists who used the results of an online test conducted by the BBC and the University of Liverpool say that some self-reflection can be good. But too much of it might lead to depression and anxiety, the most common mental health problems in the UK.

Traumatic life events such as childhood bullying and abuse were the biggest cause of anxiety and depression, according to the international study. Next are family history, income and education. And completing the list of things that make us unhappy are relationship status and social inclusion.

Having thoughts stuck on replay in her head is something a woman called Teresa (not her real name) has struggled with for years.

Teresa says: "I get angry with myself that negative thoughts run through my head. After all these years I think I should realise that they're not worth worrying about. But it feels like they are always there in the background, waiting to pop up."

She went to the doctor for help but was offered antidepressants. Teresa didn't want to go down that road and tried to develop her own coping mechanisms over the years. What makes her feel better is being in contact with nature.

The impact of mental health problems is huge. According to the World Health Organization (WHO), they affect one person in every four during their lifetime. In 2010 alone the issue is estimated to have cost $2.5 trillion globally by the World Economic Forum.

Dr Ellie Pontin, a research associate at the University of Liverpool, says it's important to understand what the findings mean for the average person.

"It's actually a really positive message and should give people hope," she says. "The way you think and deal with things can be changed."

Maybe I can find a way of sleeping better now.