SIRT1 and depressive symptom measurement: Mice with global SIRT1 overexpression displayed elevated anxiety, decreased exploratory drive, and increased susceptibility to depression by deacetylating the brain-specific transcription factor NHLH2, which increased its activity on the MAO-A promoter and therefore increased degradation of serotonin (Nordquist and Oreland, 2010; Libert et al., 2011).