Patients prefer slower movements because they are more sensitive to the energetic cost of faster, more demanding movements.210 Similar impairments in depression and schizophrenia suggest that movement speed reflects implicit evaluations of movement energy costs signalled by striatal dopamine.211 Additionally, reduced dorsal striatal DAT binding, indicative of presynaptic neuronal death, is related to anhedonia and apathy.120,212 Considered collectively, motor speed may reflect a paucity of motivational drive. The gene discussed is SLC6A3; the disease is major depressive disorder.