A study from the Department of Psychiatry and the Health Emotions Research Institute at the University of Wisconsin-Madison shows that an over-active brain circuit involving three brain areas involved in anxiety and depression is passed on from parents to offspring. This work was done using an extended family in Rhesus monkeys.

Worldwide, over 350 million people of all ages suffer from depression, according to the World Health Organization. People suffering from depression also suffer from anxiety symptoms and thus, anxiety and depressive disorders have become a major cause of disability. Anxiety and depression show a close association with subsequent substance abuse. It has previously been shown that anxiety and depression are heritable traits and that genes also determine if a person will develop stress-related disorders in later life.

The researchers in the current study endeavored to understand the specific regions in the brain that are responsible for the heritable traits of anxiety and depression. The scientists used 592 young rhesus monkeys part of a multi-generational family. They exposed young monkeys to situations that a child would encounter, such as meeting with a stranger who doesn’t make eye contact. Brain imaging studies commonly done in humans (positive emission tomography or PET) were performed in the monkeys during the meeting with strangers. Detailed studies, termed “genetic correlation,” were conducted on how anxiety-related behavior ran in a family. The results show that

• Over-activity of the prefrontal-limbic-midbrain circuit is heritable and is directly associated with extreme anxiety in early childhood and depression-anxiety later in life
• The three regions involved in anxiety and depression are survival related brain regions, namely
  • Brain stem- the most primitive part of the brain
  • Amygdala- the limbic fear center
  • Prefrontal cortex- the seat of intelligence and higher level reasoning (fully    developed only in humans and primates)
• The function of brain structure, and not its size, was inherited from parents to offspring

Regarding the findings, the senior author of the research publication Dr. Ned Kalin said to University of Wisconsin-Madison News, “Basically, we think that to a certain extent, anxiety can provide an evolutionary advantage because it helps an individual recognize and avoid danger, but when the circuits are over-active, it becomes a problem and can result in anxiety and depressive disorders.”

Understanding that parents pass on anxiety to children and knowing the exact areas of impact in the brain gives researchers an advantage in designing therapeutics for specific targets. Dr. Kalin says, “Now that we know where to look, we can develop a better understanding of the molecular alterations that give rise to anxiety-related brain function. Our genes shape our brains to help make us who we are.

By Mangala Sarkar, PhD