Serotonin in psychiatry: in vitro disease modeling using patient-derived neurons.

Several lines of evidence implicate serotonin in the etiology of multiple psychiatric disorders, especially mood disorders, such as major depressive disorder (MDD) and bipolar disorder (BD). Much of our current understanding of biological mechanisms underlying serotonergic alterations in mood disorders comes from animal studies. Innovation in induced pluripotent stem cell and transdifferentiation technologies for deriving neurons from adult humans has enabled the study of disease-relevant cellular phenotypes in vitro. In this context, human serotonergic neurons can now be generated using three recently published methodologies. In this mini-review, we broadly discuss evidence linking altered serotonergic neurotransmission in MDD and BD and focus on recently published methods for generating human serotonergic neurons in vitro.