Genetic variants in CHL1, ITGB1, and ITGB3 have also been identified as predictors of treatment-resistant depression and responsiveness to selective serotonin reuptake inhibitors (SSRIs), suggesting that the Chl1-Integrin interactions that regulate neuronal migration have further roles in serotonergic signaling (Morag et al., 2011; Oved et al., 2013, 2017; Fabbri et al., 2015, 2017; Probst-Schendzielorz et al., 2015). Here, CHL1 is linked to major depressive disorder.