were differentially regulated in subjects who had experienced severe abuse during childhood, suggesting a potentially conserved mechanism for responding to early life stressors.72 These findings are concordant with the important role of stress regulation and stress response pathways in nicotine withdrawal and smoking relapse.34, 73–78 Combined, these studies indicate that PCDH-α, -β, and -γ mRNA expression is altered in the mammalian brain in response to stimuli. Alterations that affect brain functional connectivity are thought to be associated with many neuropsychiatric disorders, including nicotine addiction.79 Future research is warranted to examine the specific effects of PCDH-α, -β, and -γ genes on brain functional connectivity.
