New research suggests that in young monkeys, some regions of the brain were more active than others when they were anxious or agitated.
“We believe that young children who have higher activity in these brain regions are more likely to develop anxiety and depression as adolescents and adults, and are also more likely to develop drug and alcohol problems in an attempt to treat their distress,” said Dr. Ned H. Kalin, the chair of psychiatry at the University of Wisconsin-Madison School of Medicine and Public Health, who led the study.
There has been a growing awareness of the problem of mental illness in childhood, including anxiety. Thirteen percent of teens have problems with anxiety, according to the National Institute of Mental Health. Untreated anxiety in childhood not only increases the chances of anxiety disorders as an adult, but can increase the risk of drug abuse, problems in school, depression and even suicide. The relative importance of genetics vs. environment in the development of anxiety is not clear.
Kalin and his team have previously published research that shows that anxious young monkeys are a good model in studying children with anxiety.
To examine the extent to which genetic and environmental factors influence anxiety, Kalin’s team studied 238 genetically related rhesus monkeys. Anxious temperament (AT) was known to occur often in this extended monkey family.
All of the monkeys in the study were assessed for the presence of AT. In both human and nonhuman primates AT is present early in life, and is characterized by increased behavioural and physiological reactivity to mildly threatening stimuli.
Positron emission tomography (PET) scans were obtained on all of the animals in the study. PET scans measure the use of glucose in the brain, and can tell how active different parts of the brain are at the time the scan is obtained.
The scans showed that there was increased activity in the central nucleus region of the amygdala, and in the anterior hippocampus parts of the anxious monkeys’ brains. While both areas of the brain have multiple functions, the amygdala is often associated with emotion and fear, and the hippocampus with memory.
In addition, the researchers could predict an individual’s degree of anxious temperament by its brain activity.
The researchers also performed genetic analysis on the monkeys and confirmed that the anxiety temperament was inherited. In addition, the increased activity in the anterior hippocampus area of the brain was genetically linked. In contrast, the increased brain activity in the amygdala was not inherited.
“We expected that all of the brain regions involved in anxious temperament would be similarly affected by genes and environment, but found that activity in the anterior hippocampus was more heritable than in the amygdala,” write the authors, “Even though these structures are closely linked, the results suggest differential influences of genes and environment on how these brain regions mediate AT and the ongoing risk of developing anxiety and depression.”
This suggests that there may be different effects of genes and environment on the function of these two regions in anxious temperament, and provides new insights into the genetic risk for anxiety and depressive disorders.
According to Kalin, “Children with anxious temperaments suffer from extreme shyness, persistent worry and increased bodily responses to stress. It has long been known that these children are at increased risk of developing anxiety, depression and associated substance abuse disorders…My feeling is that the earlier we intervene with children, the more likely they will be able to lead a happy life in which they aren’t as controlled by anxiety and depression. We think we can train vulnerable kids to settle their brains down.”
Further research in this area has the potential to develop new diagnostic and therapeutic tools for early detection and treatment of anxiety in children. Per Kalin, “Basically the idea and the hope would be we could intervene in a way that we could, more or less permanently, change a young child’s brain such that they would not have to struggle with these problems.”
Under Kalin’s leadership, researchers at the HealthEmotions Research Institute are translating these findings to humans by measuring amygdala and hippocampal function in young children who have early signs of anxiety and depression.
The study suggests that there is a tremendous opportunity to modify the environment to prevent children from developing full-blown anxiety.
The study was published in the August 12th edition of the journal Nature.