Reassuring findings on effects of anxiety and depression on cancer development

By Rebecca Jenkins

A meta-analysis challenging the theory that depression and anxiety increase the risk of developing cancer should reassure patients who feared their mental health played a part in their cancer diagnosis, experts say.

Both depression and anxiety have been hypothesised to be linked to an increased risk of cancer, but the findings of previous meta-analyses had varied greatly, researchers wrote in Cancer.

For this study, they examined data from the international Psychosocial Factors and Cancer Incidence consortium, containing information on more than 300,000 adults from Europe and North America taken from 18 prospective cohorts.

Analysing outcomes over a follow-up period of up to 26 years, researchers found no associations between depression or anxiety and cancer diagnosis overall, or breast, prostate, colorectal and alcohol-related cancers specifically.

Depression and anxiety were associated with a higher risk of lung cancer and smoking-related cancers, the researchers reported.

But these associations were ‘substantially attenuated’ when they additionally adjusted for known risk factors, including smoking, alcohol use and body mass index.

‘The results ... may help health professionals to alleviate feelings of guilt and self-blame in patients with cancer who attribute their diagnosis to previous depression or anxiety,’ they added.

Professor Emerita Phyllis Butow, from the School of Psychology at The University of Sydney, said the study was robustly designed, given it looked at future cancer diagnoses in people with and without anxiety or depression, within many large cohorts over time.

Professor Butow said it was common for people to worry that stress or difficult life events such as divorce had caused their cancer, but there was no good evidence to suggest such a link.

‘They also worry that anxiety or depression, often seen to be a result of stress, may have caused their cancer, so these results will be reassuring,’ she said.

Professor Butow, who founded the Australian Psycho-Oncology Co-operative Research Group, said a 2020 systematic review and meta-analysis had concluded depression and anxiety might cause cancer or cause its prognosis to be worse. But those researchers had said it was also possible that cancer, especially disease with a poor prognosis, caused anxiety and depression, suggesting the direction of causality was unclear.

Professor Butow suspected that if anxiety and depression did have a role to play in cancer development and prognosis it was primarily through impacting behaviour, such as treatment adherence, alcohol consumption and smoking, rather than a biological effect.

‘I would like to see future studies very carefully controlling for these variables,’ she told Medicine Today.

‘Studies should also take comprehensive mental health histories, to identify chronic or severe continuing anxiety or depression, as that is likely to have a greater role in impacting behaviour, disease development and outcomes than a short episode.’

Cancer 2023; 1-13; doi: 10.1002/cncr.34853.