Additional Study Information: Studies show that hormones affect the brain's fear extinction network, which is relevant for therapy involving exposure and response prevention (EX/RP), a first-line treatment for obsessive compulsive disorder (OCD). This study will examine the effect of delivering EX/RP to women during different phases in their menstrual cycle to determine the effects of hormones on the fear extinction network and on their OCD symptoms. Men will also be recruited for this study to further explore biological sex differences.