Study successfully treats mental illness with bone marrow transplant

Bone marrow transplants are usually used to treat life-threatening diseases like leukemia. But a team of researchers led by a Nobel Prize-winning geneticist recently used the procedure to rid mice of a psychiatric disorder - a discovery that could have huge implications for the field of mental health.

The mice suffered from a compulsion to groom excessively, to the point they would develop patches of bare skin. This is similar to a human condition called trichotillomania, a type of obsessive-compulsive disorder that causes people to pull their hair out.

"All animals spend a lot of time grooming, and what they're doing is removing pathogens," explained Mario Capecchi, a geneticist from the University of Utah who won the Nobel Prize for medicine in 2007 for his work on mouse genetics.

For people with this type of disorder, grooming goes overboard. Capecchi used the example of people who wash their hands until they bleed.

"They're not getting the feedback that says, 'Oh, my hands are clean. I can stop.'" Capecchi wondered if the disorder goes beyond psychology, and is the result of faulty immune cells.

Sure enough, the researchers discovered that microgilia - immune cells that rid the brain of dead cells - were not functioning properly in the mice.

They seemed to be communicating with synapses in the brain and affecting behaviour - something not thought possible.

Capecchi's team treated the mice with bone marrow, which makes all blood cells in the body. The critters were cured within a matter of months.

"This was a surprise," Capecchi told QMI Agency. "Who would have thought that you could treat a behaviour disorder with a bone marrow transplant?" He said this could have wider implications for a range of disorders, including depression, schizophrenia, Alzheimer's and bipolar disorder.
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While scientists have known for a long time that people with psychiatric disorders tend to have shoddy immune systems, everyone assumed the former caused the latter.

For example, it was believed depression, or the anti-depressants used to treat it, caused people's immune systems to break down.

But this study says the immune system is causing the mental-health issues, and not the other way around.
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The study is published in the journal Cell.