It's all just talk

According to the newly published study, a type of cell in the hippocampus called OLM cells may be responsible for someone’s bravery or anxiety. These neurons result in a brain rhythm compared to states found in animals that feel safe in a dangerous environment, such as secured in a hiding place with a predator in the vicinity.

Interestingly enough, these OLM cells may also explain why some people turn to cigarettes when anxious — the cells are quite sensitive to the presence of nicotine. (src)