We decided to study the PIP5K2A gene, because this gene has repeatedly been shown to be associated with schizophrenia (Schwab et al., 2006; Bakker et al., 2007; He et al., 2007; Saggers-Gray et al., 2008), and the vulnerability to develop TD is related to the likelihood to develop positive symptoms of schizophrenia. This evidence concerns the gene PIP4K2A and schizophrenia.