Anxiety May Be Genetic

Summary
Two sites in the human brain–the amygdala and the anterior hippocampus–have been said to influence emotion and psychopathology. However, no information was available on their role in characteristics like Anxious Temperament (AT or anxiety) or on whether the responsible factors were hereditary. A study conducted by researchers at the University of Wisconsin-Madison has demonstrated that abnormal metabolic activity in the amygdala and the anterior hippocampus are responsible for the development of anxiety in children and that genetic and environmental factors affect the two sites differently.

Introduction
AT in children is characterized by severe shyness in the presence of strangers, constant worry, fidgeting etc. as a response to stress. Children with AT are recognized as being at an increased risk of developing anxiety, depression and substance abuse disorders as adolescents and adults. The study conducted research in young rhesus monkeys to understand how the two brain sites were involved in anxiety. The study’s findings could help with the right approach to managing children with anxiety.

Methodology
•    A radiotracer to map brain activity was injected into 238 young rhesus monkeys.
•    The monkeys were subjected to a threat in their cage–-a human intruder who stood about 8 feet away from the cage and established no eye contact. Their behavior in such a threat-inducing situation was studied for 30 minutes.
•    Positron emission tomography (PET) scans were conducted to check for brain activity.
•    Anxiety was assessed by measuring threat-induced freezing behavior, loss of vocalizations as well as plasma cortisol concentrations.

Key Findings
•    Young monkeys from a large single family showed an inherited pattern of AT that concurred with previous studies. The monkeys that displayed anxious temperaments had a higher activity in the central nucleus of the amygdala  and anterior hippocampus areas of the brain that predicted the individual’s level of anxiety. The activity in the anterior hippocampus was more heritable than in the amygdala.
•    Genetic and environmental factors affected the two sites to different extents.
•    The risk of developing AT is more likely to be related to the hippocampus and not the amygdala.

Next Steps
This model of combining brain activity studies with behavioral studies can be used to determine genes that are responsible for development of anxiety in humans.

Conclusion
The study indicates that changes in internal (genetic) as well as external (environmental) factors affect the amygdala and the anterior hippocampus regions of the brain differently and that the anterior hippocampus region is responsible for development of AT. Also, it was found that the metabolic activity in the amygdala and hippocampus relating to levels of anxiety are indeed inherited in subsequent generations but to different extents. Further studies using the same technique of combining behavioral studies and brain scans can be used to discover genes involved in anxiety disorders. This will prove very useful in the understanding and treatment of anxiety not only in children but also in adults ultimately.

For More Information:
Heritability of Anxious Temperament
Publication Journal: Nature, August 2010
By Jonathan A. Oler, Andrew S. Fox; University of Wisconsin-Madison, Wisconsin

*FYI Living Lab Reports Are Summaries of the Original Research.