Na cai uses genetics as a tool to investigate the nature of Major Depressive Disorder, one of the most common and debilitating diseases in the world. She started her career by being the lead analyst in a genome-wide association study (GWAS) on MDD that identified the first two significant and robust genetic associations to MDD. She also discovered a replicable increase in mitochondrial DNA (mtDNA) copy number and mutations in MDD patients as compared to controls, and demonstrated that both are inducible by chronic stress in mouse models. Since then, her work has been two-pronged, one aiming to improve MDD diagnostics and resolve MDD heterogeneity, and the other focusing on molecular consequences of chronic stress. For the former, Na Cai investigated how disease definitions can impact genetic findings, and developed approaches to maximally utilize different definitions of MDD available in large datasets while preserving specificity of the findings to MDD. Her research group is currently investigating the relationship between the genetics of MDD and its symptoms, asking which symptoms are etiologically relevant to MDD, what biological pathways they capture, and how these pathways work together to cause MDD. Going forward, Na Cai is working on building and testing the genetic and biological validity of symptom-network models of MDD, and using that to inform and refine diagnostic criteria for MDD and its subtypes. For the latter, her research group is currently working on spatial-temporally resolving the molecular consequences of chronic stress in the brain using mouse models. Moving forward she will also focus on integrating their findings with brain imaging and multi-omics data from post-mortem human subjects. She aims to develop a neurological understanding of what happens during chronic stress and why, biologically speaking, it is such a big risk factor for psychiatric disorders like MDD.