Brian Brennan, MD

Brian P. Brennan, MD, MMSc

McLean Hospital Title
Harvard Medical School Title
  • Associate Professor of Psychiatry


Brian P. Brennan, MD, MMSc, is an associate professor of psychiatry at Harvard Medical School and is the medical director of the Obsessive Compulsive Disorder Institute at McLean Hospital—an intensive residential treatment facility for patients with severe OCD and related disorders. He is also the associate director of translational neuroscience research in the Biological Psychiatry Laboratory at McLean Hospital and has published extensively on the use of neuroimaging to investigate neurochemical and neurobiological abnormalities underlying psychiatric disorders such as OCD and depression.

The primary focus of Dr. Brennan’s research is the identification of novel biological targets for the development of improved therapeutics for OCD and related disorders. He has received grant funding from the National Institute of Mental Health, NARSAD, the Sidney R. Baer Jr. Foundation, and the Stanley Medical Research Institute. Dr. Brennan is involved in the teaching and supervision of psychiatry residents in the MGH/McLean Psychiatry Residency Training Program. He provides individual psychopharmacology supervision, serves as a discussant for case conferences, and lectures on the care of patients with OCD.

Research Focus:

Dr. Brennan is a clinician-scientist specializing in the care of obsessive compulsive disorder (OCD) and related disorders.

Over the course of his career, Dr. Brennan’s research has focused on the identification of novel biological targets for the development of improved therapeutics for neuropsychiatric disorders. He has designed and conducted clinical trials across all phases of drug development investigating treatments for a variety of disorders including OCD, mood disorders, anxiety disorders, eating disorders, and chronic pain disorders such as fibromyalgia and irritable bowel syndrome.

In conjunction with his clinical trials work, Dr. Brennan uses multimodal neuroimaging including magnetic resonance spectroscopy (MRS) and functional MRI (fMRI) to better understand mechanism of action, assess target engagement, and identify biomarkers of treatment response. Much of this work focuses on the use of MRS to investigate glutamatergic abnormalities in OCD and depression.

A recent focus of Dr. Brennan’s work has been the use of task-based and functional connectivity fMRI to identify discrete neural systems underlying specific symptom dimensions in OCD such as contamination/washing and responsibility for harm/checking symptoms. The aim of this work is to develop more personalized therapeutics for OCD by identifying unique symptom-specific cortical targets for neuromodulation that can be used in conjunction with current symptom non-specific treatments to enhance overall response.

Selected Publications:

Brennan BP, Hudson JI, Jensen JE, McCarthy J, Roberts JL, Prescot AP, Cohen BM, Pope HG Jr, Renshaw PF, Ongür D. Rapid enhancement of glutamatergic neurotransmission in bipolar depression following treatment with riluzole. Neuropsychopharmacology. 2010;35(3):834-46.

Brennan BP, Rauch SL, Jensen JE, Pope HG, Jr. A critical review of magnetic resonance spectroscopy studies of obsessive-compulsive disorder. Biological Psychiatry. 2013;73(1):24-31.

Brennan BP, Wang D, Li M, Perriello C, Ren J, Elias JA, Van Kirk NP, Krompinger JW, Pope HG Jr., Haber SN, Rauch SL, Baker JT, Liu H. Use of an individual-level approach to identify cortical connectivity biomarkers in obsessive-compulsive disorder. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. 2019;4(1):27-38.

PubMed search for Dr. Brennan

Education & Training

  • 1994 BA, University of Pennsylvania
  • 2000 MD, University of Pennsylvania School of Medicine
  • 2009 MMSc, Harvard-MIT Division of Health Sciences and Technology
  • 2000-2001 Preliminary Internship in Internal Medicine, Pennsylvania Hospital
  • 2001-2004 Residency in Psychiatry, Massachusetts General Hospital/McLean Hospital
  • 2003-2004 Administrative Chief Resident, McLean Hospital
  • 2005-2007 Clinical Trials Fellowship, Biological Psychiatry Laboratory, McLean Hospital
  • 2007-2009 Clinical Investigator Training Program, Harvard-MIT Division of Health Sciences and Technology/Beth Israel Deaconess Medical Center, in collaboration with Pfizer and Merck
Board Certifications:
  • 2001 Medical License, Board of Registration in Medicine, Commonwealth of Massachusetts
  • 2005 Psychiatry, American Board of Psychiatry and Neurology


Phone: 617.855.2911
Office Address: Belmont campus - Oaks Building