PRKN and attention deficit-hyperactivity disorder: Re et al. (2018) were able to generate differentiated neurons using hair-derived keratinocytes of 1 adult patient. Palladino et al. (2018) investigated a candidate gene for ADHD, PARK2, coding for a protein involved in mitochondria functioning, using human dermal fibroblasts and iPSC-derived dopaminergic neurons from patients suffering from ADHD. They found that carrying a copy number variation of PARK2 might impact mitochondrial dynamics and thereby processes important during developmental periods (Palladino et al., 2020).