Depression and anxiety may be just as bad for your health as smoking and obesity. However, cancer does not correlate with these mental health conditions. These are the main takeaways of a new study that investigates the physical health risks of these psychiatric conditions.

In the 17th century, Enlightenment philosopher Rene Descartes posited that the mind and the body were separate entities.

While this dualist idea has shaped much of modern science and thought, recent scientific advances show that the dichotomy between the mind and the body is a false one.

For instance, neuroscientist Antonio Damasio famously wrote the book he entitled "Descartes' Error" to prove precisely the point that our brains, emotions, and judgment are much more intertwined than people previously believed.

The findings of a new study may further contribute to this latter argument. Aoife O'Donovan, PhD, of the Department of Psychiatry at the University of California San Francisco, and her colleague Andrea Niles, PhD, set out to examine the effects that psychiatric conditions, such as depression and anxiety, may have on a person's physical health.

The researchers investigated the health of more than 15,000 seniors over 4 years and published their findings in Health Psychology, the journal of the American Psychological Association.

Anxiety and depression similar to smoking

The study looked at the health data of 15,418 retirees who were 68 years old, on average. The data came from a governmental study that used interviews to assess the participants' symptoms of anxiety and depression.

The participants also answered questions about their weight, smoking status, and medical conditions they had a diagnosis of. In addition, they provided information about weight recordings from hospital visits.

Of the total number of participants, O'Donovan and colleagues found that 16% had high levels of anxiety and depression, 31% had obesity, and 14% were smokers.

Those living with high levels of anxiety and depression were 65% more likely to develop a heart condition, 64% more likely to have a stroke, 50% more likely to develop high blood pressure, and 87% more likely to have arthritis than people who did not have anxiety or depression.

"These increased odds are similar to those of participants who are smokers or are obese," says O'Donovan. "However," she adds, "for arthritis, high anxiety and depression seem to confer higher risks than smoking and obesity."

Cancer not related to anxiety and stress

Of all the conditions investigated, the scientists found that cancer was the only one that did not correlate with anxiety and depression. These findings confirm previous studies, explain the researchers, but they run against the belief that many patients share.

"Our findings are in line with a lot of other studies showing that psychological distress is not a strong predictor of many types of cancer," says O'Donovan.

"On top of highlighting that mental health matters for a whole host of medical illnesses, it is important that we promote these null findings. We need to stop attributing cancer diagnoses to histories of stress, depression, and anxiety."

—Aoife O'Donovan

"Anxiety and depression symptoms are strongly linked to poor physical health, yet these conditions continue to receive limited attention in primary care settings, compared to smoking and obesity," Niles says.

O'Donovan adds that the findings highlight the "long-term costs of untreated depression and anxiety [...] and serve as a reminder that treating mental health conditions can save money for health systems."

"To our knowledge, this is the first study that directly compared anxiety and depression to obesity and smoking as prospective risk factors for disease onset in long-term studies," says Niles.

In the US, over 16 million people have had at least one episode of major depression in their lives. Also, again according to the National Institute of Mental Health, over 19% of adults in the US have had an anxiety disorder in the past year.