This is a randomized, double-blind, placebo-controlled crossover pilot study of single-dose intranasal oxytocin (6 IU and 24 IU) vs. placebo in adult men and women (aged 18 years and above) with arginine-vasopressin deficiency to evaluate the effect of oxytocin on anxiety, depression, and socioemotional functioning (Part A), with an optional randomized, double-blind, placebo-controlled 2-week repeated dose substudy of intranasal oxytocin 6 IU or placebo (Part B). Following a screening visit to determine eligibility, participants will return for three main study visits in Part A. During the main study visits, study participants will receive either oxytocin or placebo, followed by assessments of emotional behavior. In Part A, thirty participants will be equally randomized to one of six possible groups: 1. 6 IU oxytocin - 24 IU oxytocin - placebo 2. 6 IU oxytocin - placebo - 24 IU oxytocin 3. 24 IU oxytocin - 6 IU oxytocin - placebo 4. 24 IU oxytocin - placebo - 6 IU oxytocin 5. placebo - 6 IU oxytocin - 24 IU oxytocin 6. placebo - 24 IU oxytocin - 6 IU oxytocin Following completion of the Part A crossover portion of the study, in Part B participants may also choose to continue participation in an optional, randomized, double-blind, placebo-controlled substudy of intranasal oxytocin 6 IU or placebo three times a day for two weeks, followed by assessments of emotional behavior.