Among the best, repeatedly found, “cross-disorder” pleiotropic risk genes for neurodevelopmental psychiatric disorders is Transcription Factor 4 (TCF4) that has been shown to be implicated in autism spectrum disorder, major depression, and schizophrenia (Forrest et al., 2018; Pardiñas et al., 2018; Amare et al., 2019; Calabrò et al., 2020). Here, TCF4 is linked to major depressive disorder.