CHRNA4 and attention deficit-hyperactivity disorder: 2002), and later research has replicated these findings (Turic et al. 2004; Adams et al. 2004; Williams et al. 2012). Cholinergic receptor alpha subunit genes CHRNA4 and CHRNA7 have been associated with both ADHD and nicotine use. In ADHD, nAChRs containing α4 and α7 subunits are candidate genes for their role in learning and attention via modulation of striatal DA release (Kessi et al. 2022). Chronic ND is shown to upregulate α4 and α7 nAChR subunits on GABA interneurons, which is known to modulate DA transmission (Sherafat et al. 2021).