In addition to these endpoints, we also evaluated transcriptional changes in genes linked to neuronal activation and plasticity (fosb, cfos, bdnf) [50–52], genes implicated in PTSD, a psychiatric disorder heavily co-morbid with nicotine use disorder (fkbp5, brd4, crf) [12, 53–57], as well as smoking cessation outcome linked genes (nrg3 and erbb4) [58, 59]. This evidence concerns the gene BRD4 and post-traumatic stress disorder.