Behavioral regression, bipolar disorder, psychosis, and catatonia have also been reported in patients with MBD5 haploinsufficiency (also known as autosomal dominant mental retardation 1 or 2q23.1 deletion syndrome) [70, 71]; psychosis and catatonia are known to occur in a fraction of patients with Down syndrome [72–75]; and several instances of regression, psychosis/schizophrenia, and bipolar disorder were described in Tatton-Brown-Rahman syndrome, an overgrowth ID syndrome caused by DNMT3A variants [76]. This evidence concerns the gene MBD5 and Down syndrome.