Since the middle of the past century, we have serendipitously come across treatment regimens that can partially ameliorate psychosis and depression. Nonetheless, the mechanisms underlying such severe mental conditions still remain elusive. Such lack of mechanistic insight into major mental illnesses has hampered the establishment of precise diagnostic framework, precluding further discovery of fundamental treatments for these disorders. Meanwhile, understanding of the brain at the molecular level has dramatically expanded, in particular by the identification of neurotransmitters and their receptors in the second half of the 20th century.

If we retrospectively view the scientific situation when the current century started, we can recall how scientists felt serious dilemma in the lack of understanding of several mental conditions at the molecular level, although the basic molecular neuroscience had advanced. In the year 2000, a group reported a molecule with the fascinating name, Disrupted–in-Schizophrenia 1 (DISC1), based on the unique finding of a familial aggregation of major mental illnesses. 1 It was very reasonable that people suddenly jumped onto this fascinating molecular lead, given that there had been a long-term gap in understanding molecular neuroscience and psychiatry.