For women, being depressed can raise the risk of developing colorectal cancer, a new study shows.
In the study published in the American Journal of Epidemiology, researchers from Brigham and Women's Hospital and the Harvard School of Public Health analyzed data from the Nurses' Health Study, a long-term, ongoing study involving some 121,700 female nurses.
The researchers analyzed data from 81,612 women who were cancer-free at the start of the study. On two occasions four years apart, the women were screened for depression using a five-question survey that asked, for example, how often over the previous month they had felt nervous, down or happy. Based on their symptom scores, the women were divided into four categories.
About 8% of the women were classified as having high levels of depressive symptoms. While these women were more likely than the women who reported a lower degree of symptoms to be overweight, to smoke, to be physically inactive, to eat a higher-calorie diet and to consume more red and processed meat - factors which have been linked to an increase in colorectal cancer risk - they were also more likely to take vitamins, to use ASA (acetylsalicylic acid) and to be screened for colon cancer using colonoscopy or sigmoidoscopy.
Four years after the final screening, 400 of the participants had been diagnosed with colorectal cancer and another 966 were found to have colorectal adenomas, growths or polyps in the colon or rectum that can become cancerous.
After analyzing the data, the researchers found that women who reported the highest levels of depressive symptoms had a 43% greater risk of developing colorectal cancer than women with the lowest level of symptoms. Furthermore, they observed a "dose-response" relationship, which means that the more depressive symptoms a woman experienced, the higher her risk of developing colorectal cancer. The association was highest among women who were overweight.
The researchers found no association between depression and colorectal adenomas.
While the links between depression and cancer have been the subject of numerous investigations, the researchers say this is the first to focus exclusively on the relationship between depression and colorectal cancer. But the researchers add that more research is required to probe the mechanisms behind the apparent association.
In Canada, an estimated 22,000 cases of colorectal cancer are diagnosed and about 9,100 people die from it each year. But caught early, it's curable in about 90% of cases - so talk to your doctor about whether you're at risk for colorectal cancer and ask about appropriate screening measures if you are.
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