Until early 2016, scientists were left in the dark about what causes obsessive compulsive disorder (OCD) in people's brains. The mystery around this topic is in part due to the wide variety of ways OCD can manifest itself. By conducting studies with mice, scientists have found the chemical receptor in the brain that is responsible for OCD. The article, published in Biological Psychiatry in May 2016, details how scientists looked at the neural activity of mice that were bred to lack a gene called Sapap3, which, when missing, caused mice to obsessively groom themselves. With the knowledge they gathered about the Sapap3 gene, researchers went a step further — they examined the mice with obsessive grooming habits and found that the chemical receptor called mGluR5 was constantly activated in the brains of mice who exhibited OCD. Shockingly, when scientists injected these mice with a chemical that deactivates mGluR5 receptors, the mice's OCD behavior disappeared within minutes. Learn more about OCD, and other psychological disorders, with these videos.