Do antibiotics cause mental illness and stop brain cell growth?

Brain Cells At Risk: Possible Memory, Psychiatric Effects From Antibiotic Use, Reversal Is Believed Possible

A side effect of antibiotics, used to kill pathogenic bacteria, is that they also kill gut bacteria, but now, thanks to a new study on mice, scientist think that antibiotics may have another sinister side effect: they seem to also affect brain cells. The new study gives scientists reason to believe that antibiotics that are strong enough and used long enough to kill off most of our gut bacteria may also prevent the growth of new brain cells in the hippocampus. This is a section of the brain that is associated with memory, emotion and spatial navigation.

Extended use of antibiotics to treat bacterial infections or reduce colonization might impact brain function, according to senior author Susanne Asu Wolf of the Max-Delbrueck-Center for Molecular Medicine in Berlin, Germany. The new study was published in Cell Reports. The researchers involved in the study say they think they know what the link between antibiotic use and the brain might be. Wolf says that about a decade ago, they figured out that the immune system has the ability to influence the health and growth of brain cells, according to T cell research. Now, they have discovered that a type of white blood cell that acts as a communicator between the brain and the immune system, which seems to be the key to this link.

Science Daily explained that mice who were treated with enough antibiotics to wipe out intestinal microbes showed signs of a loss of neurogenesis in a section of their hippocampus that produces new brain cells throughout a person’s life. Treated mice also performed worse in memory tests. Interestingly, the mice also had “a lower level of white blood cells (specifically monocytes) marked with Ly6Chi in the brain, blood, and bone marrow.”

The researchers decided to see if the Ly6Chi monocytes were involved in the changes in neurogenesis and memory. They also compared mice that had not been given antibiotics to mice that had healthy gut bacteria levels, but low levels of Ly6Chi. Mice with low Ly6Chi levels had the same memory and neurogenesis problems as mice that had lost healthy gut bacteria. When the Ly6Chi levels were restored in mice treated with antibiotics, memory and neurogenesis improved.

“For us it was impressive to find these Ly6Chi cells that travel from the periphery to the brain, and if there’s something wrong in the microbiome, Ly6Chi acts as a communicating cell,” Wolf said, adding that mice who were then given probiotics actually were able to regain memory and begin creating new brain cells again. “The magnitude of the action of probiotics on Ly6Chi cells, neurogenesis, and cognition impressed me.”

Here is where it really get interesting and bypasses any existing scientific notions. Probiotics helped the mice’s brains, but fecal transplants used to repair the gut did not help the brain.

“It was surprising that the normal fecal transplant recovered the broad gut bacteria, but did not recover neurogenesis,” says Wolf, according to a press release. “This might be a hint towards direct effects of antibiotics on neurogenesis without using the detour through the gut. To decipher this we might treat germ free mice without gut flora with antibiotics and see what is different.”

Wolf says that they think that the immune cell link to the brain may have an affect on mood and psychiatric symptoms, as well. She says that future studies will examine the ability of probiotic treatment to affect the outcomes of these disorders and symptoms, which mirrors the hypotheses of the alternative health field that have existed for years.

The article in Cell got into further detail that has been overlooked by most of the science media coverage, explaining that additionally, the “evidence indicates that the microbiota-brain relationship plays a crucial role in the development of metabolic and mental diseases.”

[Image via Pixabay]