This chapter will provide a brief overview of anxiety disorders, traumatic disorders, and their symptoms and their treatments. Included here are descriptions of how the symptoms of anxiety disorders overlap with each other, and also with the symptoms of major depressive disorder and with the symptoms of trauma and stress-related disorders. Clinical descriptions and formal diagnostic criteria are mentioned here only in passing. The reader should consult standard reference sources for this material. The discussion here will emphasize how the functioning of various brain circuits and neurotransmitters – especially those centered on the amygdala – impact our understanding of the symptoms of fear, worry, and traumatic memories.