MeCP2 gain of function is associated with MeCP2 duplication syndrome (MDS), which causes severe mental retardation, stunted motor development, early-onset hypotonia, epileptic seizures, and progressive spasticity [81], and interestingly is also associated with mood alterations such as anxiety, depression, and an autistic-like phenotype [82]. This evidence concerns the gene MECP2 and Anxiety.