Caudate nucleus volumes and genetic determinants of homocysteine metabolism in the prediction of psychomotor speed in older persons with depression

Objective: The authors sought to determine whether caudate nucleus volumes or specific genotypes predict psychomotor slowing in older persons with depression. Method: Forty-seven persons with depression (mean age=51.8 years, SD=12.4) and 20 healthy volunteers (mean age=56.1 years, SD=9.8) underwent clinical assessments, a neuropsychological test of psychomotor speed (part A of the Trail Making Test), high-resolution magnetic resonance imaging scans, and genotyping for the apolipoprotein E ε4 allele and a mutation of the methylenetetrahydrofolate reductase enzyme. Results: Multivariate analyses revealed that psychomotor speed was uniquely predicted by age, a diagnosis of depression, right caudate nucleus volume, and mutation of the methylenetetrahydrofolate reductase enzyme. Conclusions: Psychomotor slowing, a key clinical and cognitive phenomenon in older persons with depression, is predicted by reduced caudate nucleus volumes and genetic determinants of homocysteine metabolism.