His thesis work focused on activity dependent gene regulation of neural cell adhesion molecules. Dr. Hahn directs the Neuropsychiatric Signal Transduction Program within the Center for Neurobiology and Behavior in the Department of Psychiatry. The program has a special interest in developing new research paradigms that address clinically relevant questions for psychiatric illnesses from molecular and cell biological perspectives. Currently, his laboratory program has two major avenues of research. First, he employs the olfactory epithelial biopsy approach to investigate intracellular molecular processes associated with the pathophysiology and treatment of mood disorders and psychiatric illnesses. Second, he investigates protein-protein interactions in the post-synaptic density with a focus on neuregulin 1 - erbB4 signaling in postmortem brain tissues of patients with schizophrenia. His research has been supported by Stanley Medical Research Institute, National Alliance for Research on Schizophrenia and Depression, Pharmaceutical Companies and National Institute of Mental Health.