With anxiety disorders among the most prevalent mental
illnesses in the United States, a study published in Molecular Psychiatry on Tuesday found that blocking a stress hormone in a specific part of the brain could
help treat them.
According to the National Institute of Mental
Health, anxiety disorders affect about 18 percent of the population of the
United States. Anxiety can take many forms, including generalized anxiety, obsessive-compulsive
disorder and specific phobias. Women are 60-percent more likely than men to
experience an anxiety disorder and the average age of onset is 11 years old.
The study was performed by researchers Dr. Joseph Majzoub
and Dr. Rong Zhang in the Division of Endocrinology at Boston Children’s
Hospital. They investigated the effect of blocking a stress hormone called corticotrophin-releasing
hormone in the area of the brain known as the hypothalamus.
The hypothalamus is responsible for releasing
hormones that regulate thirst, hunger, sleep and other basic functions. When
it perceives a threat, it releases stress hormones that prime the
body to respond. Fear in the face of threats is natural, but anxiety disorders
manifest as more generalized feelings of worry and tension that interfere with
Researchers have known for almost 40 years that CRH
co-ordinates the physical and behavioral stress response. Several drug companies
have developed drugs that block CRH, but the results have not been encouraging.
In a media release from Boston Children’s Hospital, Majzoub said six of
the eight completed phase II and III trials of medications that block CRH have
had negative findings, meaning they did not satisfactorily address anxiety
These earlier studies blocked CRH throughout the brain. Zhang
thought that a more focused approach might be more effective.
“Blocking CRH receptors all over the brain doesn’t
work,” Zhang said in the press release.
“We think the effects work
against each other somehow. It may be that CRH has different effects depending
on where in the brain it is produced.”
So Zhang and Majzoub removed the CRH gene from the nerve
cells of mice, targeting only those cells in the hypothalamus. Hormone
secretion was reduced as expected, but researchers were surprised to find that anxiety
behaviors were also reduced. So mice were less fearful and more willing to
explore areas they might otherwise avoid, such as an elevated platform, an open
field, and brightly lit areas.
“It was a very robust finding: Every parameter we
looked at indicated that this animal was much less inhibited,” Majzoub said in
Dr. Mark Pollack, chairman of the department of psychiatry
at Rush University Medical Center, told AMI Newswire the results
are interesting and he knows of no other studies examining the potential of
blocking CRH production this way.
“Given that CRH-blocking agents that work broadly across the
brain have thus far not been reliably effective when tested for anxiety and
depression, the challenge will be to develop and test agents that work specifically
in the hypothalamus to see if their anti-anxiety and antidepressant effects may
be more robust,” Pollack told AMI.
Current treatments for anxiety include psychotherapy,
particularly cognitive behavioral therapy, which teaches the patient to think
and behave in ways that help them overcome anxiety, and medications such as
antidepressants, bonzodiaxepines and beta blockers, which generally reduce the
symptoms of anxiety.
The CRH study represents a potential new direction for treatment,
but more study is needed before it can be used on humans.
“Blocking just certain neurons releasing CRH would be
enough to alter behavior in a major way,”
Majzoub said in the release.
“We don’t know how to do that, but at least we have a starting