In the current study, two mtDNA SNPs in the MT-ND4 gene---m.11299 T > C (haplogroup K defining marker) and m.11467 A > G (super UK defining marker), although not the lead mtDNA SNPs---were significantly associated with general neuroticism and with worry/vulnerability, respectively, and so may provide a partial explanation for the link between neuroticism and Alzheimer’s disease. This evidence concerns the gene MT-ND4 and early-onset autosomal dominant Alzheimer disease.