Depression and anxiety are not linked to a greater overall risk of cancer, though researchers did see an association with lung cancer and smoking-related cancers, according to study findings published in the journal Cancer.

“Our results may come as a relief to many patients with cancer who believe their diagnosis is attributed to previous anxiety or depression,” Lonneke van Tuijl, PhD, of the University Medical Center Groningen in the Netherlands, said in a press release. “However, further research is needed to understand exactly how depression, anxiety, health behaviors and lung cancer are related.”

Unhealthy behaviors arising from depression and anxiety, along with other biological factors, could have some effect on the development of malignancies. But thus far, research has failed to firmly establish whether these mental health conditions are linked to a higher risk of cancer, and prior studies have yielded mixed results.

Van Tuijl and her colleagues sought to determine whether depression and anxiety were predictors of future cancer risk. Using data from the Psychosocial Factors and Cancer Incidence consortium, the research team analyzed links between depression, anxiety and the incidence of various types of cancer.

The consortium includes data from 18 cohorts with more than 300,000 adults in the Netherlands, Canada, Norway and the United Kingdom. The database includes assessments on depression, anxiety and cancer incidence.

In a study population of 319,613 people with more than 3 million person-years of follow-up, 25,803 people developed cancer. During a follow-up period of 26 years, the researchers found no link between depression or anxiety symptoms or diagnosis and the overall risk of cancer.

Specifically, they saw no link between depression or anxiety and the risk of developing breast cancer, colorectal cancer, prostate cancer or alcohol-related cancers. However, they found that depression or anxiety were associated with a 6% higher risk of lung cancer and other smoking-related cancers. This higher risk was greatly reduced once the researchers took into account body mass index, smoking and alcohol use as well as other cancer-related risk factors.

“Depression and anxiety are not related to increased risk for most cancer outcomes, except for lung and smoking-related cancers,” the study authors concluded. “This study shows that key covariates are likely to explain the relationship between depression, anxiety and lung and smoking-related cancers.”

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