An animal study conducted in 2009 in The Journal of Neuroscience found that fibroblast growth factor 2 (FGF2), a key chemical involved in brain development and regeneration, may contribute to mood disorders in some people.
Results are helping scientists pinpoint the underlying cause of why some people are predisposed to anxiety and depression.
Anxiety and Depression, and Low Levels of Brain Cell Growth Factor
According to the National Institute of Mental Health, approximately 40 million Americans adults have anxiety disorders, and 14.8 million suffer from major depression. Many people have both anxiety and depression, suggesting that the two disorders may share common underlying causes.
Researchers found in the 2009 study that FGF2 increases the survival rate of new cells in a brain region called the hippocampus which may lower anxiety. Depression and anxiety decreases the production and incorporation of new brain cells, a process called neurogenesis.
Findings showed that while high-anxiety rats produced the same number of new brain cells as low-anxiety rats, highly anxious rats had a lower survival rate of new brain cells compared to low-anxiety rats. Treatment with FGF2 restored brain cell survival.
Although previous human studies led by the senior author, Huda Akil, PhD, at the University of Michigan found that severely depressed people had low levels of FGF2 and other related chemicals, it was unclear whether low FGF2 was the cause or effect of the disease.
The new 2009 study led by Javier Perez, PhD also at the University of Michigan, examined FGF2 levels in rats selectively bred for high or low anxiety for over 19 generations. Consistent with human depression studies, the researchers found lower FGF2 levels in rats bred for high anxiety compared to those bred for low anxiety.
Reducing Anxiety With Environmental Enrichment, Lifestyle Changes
The research revealed another interesting finding: changing or stimulating the environment lowers anxiety by increasing FGF2 levels. Perez and colleagues gave the high-anxiety rats a series of new toys which reduced anxiety behaviors and increased their levels of FGF2. In addition, FGF2 treatment alone reduced anxiety behaviors in the high-anxiety rats. The implications suggest that simply changing one's environment or lifestyle may reduce anxiety because doing so increases FGF2 levels.
"We have discovered that FGF2 has two important new roles: it's a genetic vulnerability factor for anxiety and a mediator for how the environment affects different individuals. This is surprising, as FGF2 and related molecules are known primarily for organizing the brain during development and repairing it after injury," Perez said.
The findings may help researchers develop new pharmaceuticals that don't have the sedative effects many anti-anxiety and anti-depressant medications have. The new drugs will more accurately target the true underlying causes, explains Pier Vincenzo Piazza, MD, PhD, Director of the Neurocentre Magendie an INSERM/University of Bordeaux institution in France, an expert on the role of neurogenesis in addiction and anxiety who was not involved in the current study.
Implications for Reducing Anxiety and Fear With Exposure Therapy
FGF2 may also increase the effectiveness of exposure therapy in individuals. Exposure therapy is a behavior therapy where people are exposed repeatedly to whatever triggers their anxiety or panic. Therapists exposure the patient to their fear triggers until the person becomes very comfortable with the anxiety-provoking situation. Extinction therapy is the term used in the laboratory setting.
In the 2010 Australian study, "Fibroblast Growth Factor-2 Enhances Extinction and Reduces Renewal of Conditioned Fear," rats were trained to fear a white noise. They elicited a fear response by freezing in place. The following day researchers extinguished the rats' learned fear to the white noise through repeated exposure.The test group received systemic injections of FGF2. The test subjects that received the FGF2 injections were less likely to have a fear relapse when the heard the white noise. Their relapse rate was even lower than rats given a double dose of extinction training.
The results of the FGF2 study may help scientists better understand how neurogenesis, cell birth and integration in the adult brain contributes to anxiety and depression in individuals. Findings may help researchers develop new, more targeted drugs to treat mood disorders. In addition, FGF2-based medication may decrease relapse rates in individuals who undergo exposure therapy for anxiety and panic attacks.
Sources:
Society for Neuroscience (2009, May 13). "Brain Chemical Reduces Anxiety, Increases Survival Of New Cells." ScienceDaily. Retrieved February 16, 2010, from http://www.sciencedaily.com /releases/2009/05/090512193229.htm
Graham BM, Richardson R, Neuropsychopharmacology. (2010 Feb 3). "Fibroblast Growth Factor-2 Enhances Extinction and Reduces Renewal of Conditioned Fear," School of Psychology, The University of New South Wales, Sydney, NSW, Australia.
Laura Owens - Laura Owens has a B.S. in Psychology from Rollins College & U of FL. She is a freelance writer with expertise in motivation & wellness.
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