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Tumors spur depression

Tumors can cause classic symptoms of depression in rats, according to linkurl:a new study published online in PNAS;http://www.pnas.org/content/early/2009/05/15/0811949106.abstract this week. Image: linkurl:Understanding Animal Research;http://www.understandinganimalresearch.org.uk/ "What's really cool about this paper is that it shows without a doubt that there are depressive-like behaviors induced in these rats before these rats become [sick]," said linkurl:Keith Kelley,;http://www.iib.uiuc.e

By | May 18, 2009

Tumors can cause classic symptoms of depression in rats, according to linkurl:a new study published online in PNAS;http://www.pnas.org/content/early/2009/05/15/0811949106.abstract this week.
Image: linkurl:Understanding Animal Research;http://www.understandinganimalresearch.org.uk/
"What's really cool about this paper is that it shows without a doubt that there are depressive-like behaviors induced in these rats before these rats become [sick]," said linkurl:Keith Kelley,;http://www.iib.uiuc.edu/faculty/faculty/k_kelley.cfm an immunophysiologist at the University of Illinois at Urbana-Champaign, who was not involved in the research. Researchers have long known that individuals suffering from chronic illness are at a greater risk of depression, but whether it was a direct cause of the illness or a psychological reaction to being sick was unclear. "By using this animal model of cancer we were able to isolate just the physiological effects of the tumors from the psychological effects that you get in human studies," said linkurl:Leah Pyter,;http://home.uchicago.edu/%7Epyter/ a behavioral neuroscientist at the University of Chicago, who led the study. "The tumors themselves are sufficient to induce depression." Pyter and her colleagues induced mammary tumors in rats using a chemical carcinogen known as N-nitroso-N-methylurea (NMU). In a forced swimming test, the rats with chemically induced tumors spent more time floating instead of swimming compared with healthy controls, a classic sign of depression. And while healthy rats prefer weak sugar water to tap water, the rats with tumors showed no such preference. The rats exhibited these depressive-like behaviors well before they showed any overt signs of illness from the tumors themselves. They showed no difference in eating habits or social behavior, and they did not lose weight, like rats with an induced acute infection often do. This study "supports what we've been saying for years: that sickness can be dissociated from mood changes," Kelley said. The rats with tumors showed a boost in levels of cytokines known to mediate behavioral changes after bacterial infection or brain trauma, both in the plasma and in the hippocampus, a brain region associated with depression. This supports the notion that these cytokines regulate the behavioral changes the researchers saw, though how exactly the cytokines elicit this effect is not yet clear. To make matters worse, Pyter said, her findings suggest that the cytokine levels may be further misregulated because of the cancer's effect on the stress response pathway. Rats with tumors had a reduced increase in the stress response hormone corticosterone after exposure to a stressor. "Ordinarily glucocorticoids suppress cytokines," Pyter said. Low levels of glucocorticoids could hinder this suppression, which "could exacerbate the effects of cytokines on the brain and behavior." The next step is to start to figure out the mechanism by which the cytokines trigger these behavioral changes, Pyter said. Also, she noted, many chemotherapies are cytokine-based, and the findings may help doctors decide when those therapies would be appropriate for cancer patients.
**__Related stories:__***linkurl:A Master Regulator in the Brain;http://www.the-scientist.com/blog/display/54634/
[October 2006]*linkurl:Signal Blues;http://www.the-scientist.com/article/display/14019/
[25th August 2003]*linkurl:Mixing Religion and Health: Is it Good Science?;http://www.the-scientist.com/article/display/18487/
[29th March 1999]
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Comments

Avatar of: PAUL STEIN

PAUL STEIN

Posts: 23

May 19, 2009

Remember the recent popular press sensation over the dogs that can smell cancer? It's not magic. (Dogs can't do magic.) So what are the dogs smelling? Perhaps elements of this research can shed light on it, possibly leading to advanced diagnostics to catch those horrid diseases in their most early stages.
Avatar of: Colette Bouchez

Colette Bouchez

Posts: 2

May 19, 2009

Could it be possible that depressive symptoms are earliest markers of tumor development? Should we be having blood workups and MRIs before we dole out prescriptions of Prozac? This is particularly important since some antidepressants have been linked to increased risks of cancers. Could they be stimulating growth of smaller tumors already in the works? Interesting paper - we need more on this!
Avatar of: Jennie Burke

Jennie Burke

Posts: 3

May 19, 2009

Could we be seeing the effect of infection such as M.fermentans or M.hominis in cancer patients who are depressed ? Studies have shown significant levels of infection with Mycoplasma's in tumour tissue of varying cancers. It is also known that CFS patients with Mycoplamsa infections have a high level of depression which often resolves with antibiotic treatment.
Avatar of: Wolf Kirchmeir

Wolf Kirchmeir

Posts: 1

May 19, 2009

From the article:\n\nThis study "supports what we've been saying for years: that sickness can be dissociated from mood changes," Kelley said. \n\nSurely the study supports the notion that sickness can _not_ be dissociated from mood changes.\n\nO'wise adds to the data on the connection between biochemical (physiological) changes and mood changes.\n\ncheers,\n\nwolf k.\n
Avatar of: Zhang Junjie

Zhang Junjie

Posts: 2

May 19, 2009

The study based on the assumption that the rats didn't know that they will suffer from the cancer. But somehow I doubt about this point, since human can predict the heath condition of oneself, why not a rat?
Avatar of: Jef Akst

Jef Akst

Posts: 28

May 20, 2009

I'd like to clarify what Dr. Keith Kelley meant in the following quote:\n\nThis study "supports what we've been saying for years: that sickness can be dissociated from mood changes," Kelley said. \n\nBecause the depressive-like behaviors were seen in the rats *before* they actually exhibited any signs of feeling sick, mood changes can be instigated by the physiological effects of the tumors themselves, not any sort of psychological response to getting sick. Therefore, this study does indeed show that mood changes can be dissociated from sickness.
Avatar of: mark lewman

mark lewman

Posts: 1

May 26, 2009

thanks for the review

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