Cadherin-13 (CDH13) is implicated in multiple neurodevelopmental disorders, such as autism spectrum disorders (Sanders et al. 2011, 2015), attention-deficit/hyperactivity disorder (ADHD) (Lasky-Su et al. 2008; Lesch et al. 2008; Neale et al. 2010), major depressive disorder (Edwards et al. 2012), and substance use disorders (Hart et al. 2012; Treutlein et al. 2009; Uhl et al. 2008). This evidence concerns the gene CDH13 and major depressive disorder.