The investigators believe that ketamine may be effective in reducing symptoms of OCD due to its ability to decrease the activity of a specific brain chemical called glutamate. Previous studies have shown that people with OCD can have abnormal levels of glutamate in their brains. This is the first time that intranasal ketamine is being studied in people with OCD. However, studies have been done in the past using intravenous (IV; through a needle into a vein in your arm) ketamine in people with OCD, and intranasal ketamine has been studied in people with other psychiatric conditions.