Does stress cause cancer

In a recent post, Dr. Travis Bradberry discussed the impact of a stressful job. According to Dr. Bradberry, analyses of multiple studies have established that the stress from unstable and/or demanding jobs leads to poor health. But does this include cancer?
 

There has been a lot of confusion whether stress causes cancer. A search of evidence-based medicine resources will inform you that if there is any evidence for such connection, it is slim and weak. The difficulty of proving causation comes from the many factors that may influence cancer development, as well as from the fact that the development of cancer takes years, and measuring stress during decades of life is challenging. Some researchers have proposed that stress allows for cancer development by weakening the immune system. This hypothesis is based upon the current knowledge that a functional immune system might be able to launch a response against cells with mutations. The evidence for the direct cause and effect in this scenario is yet to be provided.
 

However, one link between stress and cancer is quite tangible. It is based upon the length of the telomeres. What is this, you may ask. Our genes are made of DNA, and this DNA forms the chromosomes in the cells of our bodies. Each of our chromosomes is protected at both ends with sequences called telomeres. As our cells duplicate (divide), the telomeres shorten. Shortening of the telomeres is equivalent to aging and it is not a good news: once the telomeres are of critical length, our cells stop dividing (this period is called senescence). However, changes (mutations) in a few genes may allow the cells to continue dividing. During such divisions, the chromosomes without their protective telomeres are subject to damage. The loss of chromosomal integrity may lead to the birth of cells with abnormal growth, and eventually, to cancer.
 

The described process partially explains why we are more prone to develop cancer at older age. The other pathway through which age contributes to cancer is the accumulation of random changes in our DNA during cell division; some of these changes (mutations) could contribute to cancer. Stress may not affect this mutational pathway; however, it may precipitate the aging (shortening) of the telomeres and thus, increase the risk of impaired chromosome integrity. Stress could do this by affecting the activity of an enzyme called telomerase. When functional, this enzyme counteracts to a certain extent the telomere shortening in special (adult stem) cells in our bodies. Stress hormones (e.g., cortisol) slow down the activity of the enzyme telomerase, making it more ineffective in preventing the telomere shortening. The fact that psychological stress shortens the telomeres faster than expected for a particular age was demonstrated with two groups of mothers: mothers of healthy children (low-stress group) and mothers of children with chronic illnesses (high-stress group). The study established that compared to the low-stress group, the high-stress group of mothers exhibited shortening of the telomeres that was equivalent to 9 – 17 additional years of age. Therefore, high stress may bring people closer to the catastrophic event when the chromosome integrity is endangered.
 

To summarize, the more stress we experience, the more cortisol we release, the more ineffective the enzyme telomerase is, the shorter the telomeres become, and the chance of chromosomal damage increases. Once our chromosomes and certain genes on them are damaged, there is a high risk of cancer development. In a future study, I would like to see a comparison of the telomere length between two groups: people with low-stress jobs and people with demanding and/or uncertain jobs.I bet the second group will exhibit shorter telomeres after adjusting for age. 

Until such study is conducted, we should remember that cancer is a result of the combined assault of age, environment, lifestyle choices, inherited genetic changes, and that stress may precipitate the process of cancer development. So, breathe deep, meditate, re-play the best moments of your life in your imagination, seize the moment through mindfulness, and laugh with the Horrible Bosses movies.