Apoptosis

"Apoptosis is the process of programmed cell death (PCD) that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, loss of cell membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation."

"Neuroimaging studies of individuals with bipolar disorder or other mood disorders also suggest evidence of cell loss in these same brain regions. Thus, a suggested cause of bipolar disorder is abnormal programmed cell death, or apoptosis, in critical brain circuitry that regulates emotion."