Depression and anxiety do not actually raise one's risk of cancer, according to a recent study.
This research debunks decades of misconceptions, with it having long been hypothesized that these mental illnesses would be linked to an increased risk of developing cancers.
The findings of this study were published in the peer-reviewed academic journal CANCER.
It's all in your head: Why cancer isn't linked to anxiety and depression
For many years, scientists had been theorizing that depression and anxiety make one more likely to develop cancer. This theoretically could have happened in a number of different ways, such as impacting overall health or inducing mutations.
This was examined in prior studies, but their outcomes varied between showing a positive correlation to showing no link whatsoever.
However, these have always been limited and thus never conclusive. Part of these limits are due to overly broad scopes by focusing on cancer in general, not utilizing all the data by not including null findings and a lack of consistency in measuring depression and anxiety.
This time, though, the researchers behind this study – itself a meta-analysis covering studies from the US, UK, Canada, Norway, and the Netherlands – decided to overcome many obstacles by way of using individual participant data (IPD) instead of just other studies.
This has some notable advantages over the other studies that came before it. Specifically, it includes all the data, rather than just the end result published information used in studies, and it also allows for more consistency in measuring depression and anxiety.
But the researchers also included another variable into the mix: Lifestyle risk factors, such as tobacco and alcohol.
Overall, the researchers were looking at the four most prevalent types of cancers – breast cancer, lung cancer, prostate cancer, and colorectal cancer – as well as cancers linked to tobacco and alcohol. In order to test this, they managed to get data from the Psychosocial Factors and Cancer Incidence consortium, which collects data from 18 different study groups in four countries, spanning over 300,000 adults.
Initially, the researchers behind this study had, like most scientists, hypothesized that depression and anxiety would result in an increased risk of cancers of all kinds.
However, what they found is that this isn't actually the case. Rather, for almost all types of cancers – specifically breast cancer, prostate cancer, colorectal cancer, and alcohol-related cancers – there was no real meaningful link with anxiety and depression.
The outliers, though, were lung cancer and tobacco-related cancers. However, there is also more nuance to this than may initially seem.
While depression and anxiety did appear to have a higher risk for these types of cancers, it was just a six percent increase. Not only that, but the actual number may be much lower, once they took into account other risk factors such as tobacco and alcohol usage.
Essentially, they say that anxiety and depression may lead to certain lifestyle behaviors such as alcohol and tobacco use, which themselves can be detrimental, but not that it is necessarily the anxiety and depression that is doing it.
That isn't to say depression and anxiety don't have any other adverse health effects. Several studies have indicated that depression and anxiety can cause a degree of memory loss, and other studies have shown that they can cause other forms of cognitive impairment.
Depression has also been long linked to heart disease. While less research on the subject exists, other researchers have also pointed out connections between heart disease and anxiety.
Further, the fact that depression and anxiety are both linked to unhealthy lifestyle risk factors such as unhealthy eating habits, lack of physical activity, high-stress conditions, and the use of substances like alcohol, tobacco, and narcotics can lead to other severe health issues down the line.
In addition, the increased risk of lung cancer, however slight it may be, is still there, and the researchers say more studies are needed to investigate just how linked depression, anxiety, and lung cancer may be.