People who develop cancer may have an increased risk of death if they also suffer with anxiety and depression, a new study has found.

These mental health conditions have already been linked to increased rates of heart disease, but until now, when it comes to cancer, the results have been unclear.

UK and Australian researchers decided to investigate this further. They analysed 16 studies from England and Scotland, involving over 163,000 people aged 16 and older. All were cancer-free at the start of the studies.

The participants were monitored for an average of just over nine years and during that time, their levels of psychological distress (anxiety and depression) were monitored.

Other factors which may have influenced the results, such as age, smoking status and socioeconomic status, were taken into account.

"After statistical control for these factors, the results show that compared with people in the least distressed group, death rates in the most distressed group were consistently higher for cancer of the bowel, prostate, pancreas and oesophagus, and for leukaemia," explained the study's lead author, Dr David Batty, from University College London.

The researchers acknowledged that the findings are observational so no firm conclusions about cause and effect can be drawn. However, they believe that this study adds to the growing body of evidence which suggests that anxiety and depression could have a major impact on certain diseases.

"Our findings contribute to the evidence that poor mental health might have some predictive capacity for certain physical diseases," Dr Batty said.

Details of these findings are published in the British Medical Journal.