CD4 and Anxiety: For example, decreased expression of the MT‐CO1 gene resulted in energy metabolism deficiency while decreased expression of JUN and FOS genes led to impaired proliferation.[39, 40] This explanation aligns well with an animal study where the investigators showed that stress‐induced mitochondrial fragmentation in CD4+ naive T cells led to excessive production of xanthine into the brain, which resulted in anxiety‐like behavior.[7]