Major depressive disorder (MDD) is an important public health problem affecting 350 million people worldwide. After decades of study, the pathophysiology of MDD remains elusive, resulting in treatments that are only 30-60% effective. This review summarizes the emerging evidence that implicates impaired mitochondrial bioenergetics as a basis for MDD. It is suggested that impaired mitochondrial bioenergetic function contributes to the pathophysiology of MDD via several potential pathways including: genetics/genomics,
inflammation, oxidative stress, and alterations in neuroplasticity. A discussion of mitochondrial bioenergetic pathways that lead to MDD is provided. Evidence is reviewed regarding the mito-toxic or mito-protective impact of various
antidepressant medications currently in use. Opportunities for further research on novel therapeutic approaches, including mitochondrial modulators, as stand-alone or adjunct
therapy for reducing depression are suggested. In conclusion, while there is substantial evidence linking mitochondrial bioenergetics and MDD, there are currently no clear mitochondrial phenotypes or
biomarkers to use as guides in targeting
therapies beyond individuals with MDD and known
mitochondrial disorders toward the general population of individuals with MDD. Further study is needed to develop these phenotypes and
biomarkers, to identify therapeutic targets, and to test
therapies aimed at improving mitochondrial function in individuals whose MDD is to some extent symptomatic of impaired mitochondrial bioenergetics.