expression [121]. It is also important to note that several recent studies, including seminal work by Feng, Nestler, and colleagues [122,123] have investigated the role of Tet1 and 5-hydroxymethylcytosine (5-hmc) cocaine addiction using animal models. These studies are important because demethylation, in addition to methylation, plays a role in gene regulation in substance use disorders. Unfortunately, these literature reviews and our own are limited by the lack of studies using peripheral tissues from living, human subjects in order to ascertain potential epigenetic biomarkers for psychostimulant use disorders. Review of these articles and our PubMed search did not find any studies using Illumina arrays that met those criteria. Therefore, at this time, we conclude that there is no epigenetic finding with clear potential for clinical translation for the assessment of psychostimulant use disorders, though there is certainly an important public health need for the development of these.
