There are already examples of altered NEFH levels in brain tissue from individuals with schizophrenia (Pinacho et al., 2016) or alcoholism (Iwamoto et al., 2004); altered levels of SYT2 mRNA in schizophrenia (McMeekin et al., 2016); and association of SYT2 with both attention-deficit/hyperactivity disorder (Sánchez-Mora et al., 2013) and cocaine dependence (Fernàndez-Castillo et al., 2012). Here, SYT2 is linked to attention deficit-hyperactivity disorder.