During early stage of brain development, 5-HT transporter (Serotonin transporter, SERT) dependent raphe nucleus-prefrontal cortex loop is associated with many neurodevelopmental disorders (Witteveen et al., 2013), including autism, depression, anxiety, obsessive-compulsive disorder and other neuropsychiatric diseases. The gene discussed is SLC6A4; the disease is obsessive-compulsive disorder.