 This video was a collaboration between me and Psych2Go, please go check out their channel, they have some really cool videos about psychology and other topics. What's the most common mental disorder in the United States? Depression? Bipolar disorder? Autism? It's actually anxiety. This affects 40 million adults in the US, 18 and older, or 18% of the population, but how does anxiety come about? The University of Wisconsin-Madison found that anxiety could be inherited. They went further into their studies using an extended family of rhesus monkeys to examine which regions of the brain were involved. First, let's go back to 1969 where developmental psychologist Mary Ainsworth performed an experiment known as the strange situation. In this experiment, young children were introduced to a mildly stressful situation being left alone with a stranger. Don't worry, the stranger was actually a research assistant. Researchers were then able to derive the different temperaments of the children when they were in that stressful situation. Children either had a secure temperament or an anxious temperament when paired with a stranger. Researchers at the University of Wisconsin-Madison did the same experiment to rhesus monkeys, scanning the brains of around 600 young monkeys, both with and without anxious temperaments, when exposed to a stranger for 30 minutes. They found three parts of the brain linked to inherited anxiety. The prefrontal cortex, the limbic system, and the amygdala in the middle of the brain. These areas were shown to have an overactive connection, which in turn links to an increased risk of developing anxiety or depression. Kaylin, senior author of the study, explains what we find is more activity in the anxious brains. It's as if the parts of the brain that we have evolved to deal with normal threats have gone super critical, responding to mild threats as if they were major. Researchers were also able to trace the inheritance of anxiety, discovering 35% of the variations of anxiety can be explained by genetics while the other percentage is determined by environment. Kaylin explains, 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 overactive, it becomes a problem and can result in anxiety and depressive disorders. So what are your thoughts on anxiety? Do you have anxiety? Let us know in the comments down below.