Bipolar Disorder

Abstract

Bipolar disorder has attracted considerable research interest from diverse neurobiological approaches. This chapter summarizes selected morphological, genetic, epigenetic, cellular, and behavioral findings, including those from animal studies. Genome-wide association studies have identified dozens of candidate risk genes, each contributing only a small amount to the heritable risk of bipolar disorder. Environmental factors contribute at least as much as an individual's genetic vulnerability to the risk of bipolar disorder. Genetic and epigenetic factors together cause a range of subtle changes in neurotransmission and intracellular signal transduction, contributing to short-term behavioral changes such as mania or depression, as well as to long-term neuroprogression as observed in postmortem brains or by neuroimaging. These changes interact in both directions with the body's endocrine regulatory systems; dysfunction of hypothalamic-pituitary adrenal and thyroid axes may be the consequence of neuronal dysfunction, but may also affect gene transcription and the disease process.