Saturday, June 9, 2012

Can an Anxious Heart lead to Cancer (revised).

Who knew an anxious heart could have a link to cancer?
Over the winter break I browsed through a book entitled, Healing Begins with the Sanctification of the Heart by Dr. Strydom, a Zimbabwean lady who got her training and qualification to be a medical doctor in South Africa. Dr. Strydom, in her insightful book discusses how anxiety and stress can be detrimental to one's health. According to her research, stages 2 & 3 of stress (contributors to prolonged stress) cause excessive production of stress hormones in the human body including ACTH- 'the fear hormone' and cortisol. Cortisol in excessive amounts kills T cells of the immune system, and when this happens T & B cells go out of balance and B cells become overactive and begin to produce excessive antibodies, this then means that the immune system no longer functions efficiently and that the individual in question becomes more susceptible to attack by bacteria and viruses. I would like to venture further and hypothesize that knowing what we previously learnt in lecture about some viruses causing cancer, I believe that anxiety can indirectly lead to cancer via the transformation of viruses and v-oncogenes which are not destroyed by the immune system. Furthermore, we know that one of the hallmarks of cancer involves evading immune system destruction (Hanahan, Weinberg), therefore, in this case, if the immune system is already down or functioning at a less than efficient level, cancer cells may just better thrive in such an environment because a weak immune system won't be able to efficiently ward off viruses and cancer cells.

I then recently found an article from Stanford School of Medicine about a study conducted by Firdaus Dhabar and colleagues entitled, Anxiety increases cancer severity in Mice. In the study, hairless mice were exposed to UV rays for 10 minutes, 3 times a week, for 10 weeks. It was noted that the nervous mice (ones with an inclination towards restraint and safety) came down with more tumors and invasive cancer. In the study, it is also pointed out that consistent anxiety led to 'sensitivity to chronic stress and a dampaned immune system' just like Dr. Strydom notes in her book.
Another interesting fact from the study to note was that the nervous mice had higher levels of T-cells and were making less chemical signals to prompt the immune system to attack tumors that had developed due to exposure to UV light. The researchers also looked at the production of another hormone, corticosterone, they found that the levels of this hormone were 'cranked up' in the nervous mice. Furthermore, although all the mice, inanxious and anxious eventually developed cancer, only the anxious mice had more tumors and were the only ones which develop invasive forms of cancer.

Tumor infiltrating T cells were quantified in low- (white bars) and high- (black bars) anxiety mice at week 31. Numbers of tumor infiltrating cells that are known to be protective (Th and CTL) or harmful (Treg) in the context of SCC were quantified. Since overall biological function is ultimately influenced by relative proportions of counteracting cells, we also examined the effects of anxiety phenotype on the ratios of protective versus harmful factors: Th/Treg, CTL/Treg, and (Th + CTL)/Treg. The number of positive cells per standardized field was counted by a blinded observer. Five fields at 60x were analyzed per stained tumor section per mouse. Data are expressed as mean ± SEM. Statistical trends (* p < 0.09) and significant differences (** p < 0.05) are indicated. Outcomes were optimally Box-Cox transformed prior to analysis. For each outcome, means were compared between groups using a two-sample t-test with Satterthwaite adjustment for unequal variances.

The graph above- in Figure 4 shows.- 'Effects of anxiety phenotype on tumor infiltrating helper (Th), cytolytic (CTL), and regulatory (Treg) T cells', from a similar study done on anxious and non-anxious mice, it shows the same correlation- namely an increased risk for the development of tumors in anxious mice.

This model was labelled as 'valuable' by the researchers because, 'it closely mimics human skin cancer'(Firdaus) and it appears to suggest that this same phenomenon would be observed in human cases although at the time the article was written, it appears that this model had not yet been tested on humans. It is important to note that mice and humans are different on so many levels and I think it is important not to get too paranoid on this issue, I do not personally believe that all prolonged anxiety will lead to a weakened immune system, I believe like Dr. Strydom that it depends on who you are and how you react to stress. I also wouldn't immediately take all of Dr. Strydom's facts as absolute truth because I have not found her work to have undergone rigorous peer review, therefore while her work is very plausible, I believe that I would buy into her conclusions even more after her work undergoes rigorous and professional reviews and critiques which come out optimistic.
The data from the various studies and sources of information(stanford and additional graph) I looked at are very convincing. The graph dealing with anxious and non-anxious mice clearly shows a significant increase of tumor incidences in anxious mice, which to me signals that the researchers are on to something as far as anxiety and tumor development is concerned.
Overall, I enjoyed this this study because it appears to provide very logical answers and links to the implications of an issue which has affected many of us from one time to another, as a person who has experienced panic attacks and anxiety before, this research was invaluable, it opened my eyes to the implications that simple things like anxiety can pose to affect our health. This study also illustrated the power of  the immune system; during the first few weeks of our class, Dr. Islas told us that the immune system can ward off cancers, after seeing the immune system's power demonstrated in Dr. Strydom's book and in this article, I do not doubt this. I also believe that drugs and therapies should work around the immune system in an attempt to cure and avoid cancer. Think of the possibility of treating cancers with no side effects whatsoever, that would be so good, especially for the patient. I am also very interested to see what the results will come out like in tests based on anxiety in human cases, will the hypotheses by the authoritative figures above really hold true? Time can only tell.