A. Diefenbach, Ph.D.

About the researcher:

Before joining North Shore-LIJ, Dr. Diefenbach was Associate Professor of Urology and Oncological Sciences at the Icahn School of Medicine at Mount Sinai, New York. Dr. Diefenbach serves on the editorial board of the Annals of Behavioral Medicine and Cancer Epidemiology, Biomarkers, and Prevention. He is a frequent reviewer for the Department of Defense, the Veteran’s Administration and the National Institutes of Health, where he served as a permanent member of the Behavioral Medicine and Intervention study section (BMIO).  He was elected to Fellow status of the Society of Behavioral Medicine and the Academy of Behavioral Medicine.  He has been serving as secretary/treasurer of the Society of Behavioral Medicine since 2012.

Dr. Diefenbach is a behavioral scientist with a degree in Health/Social Psychology whose research focuses on how patients make treatment decisions under distressing and uncertain medical conditions. He has investigated basic psychological mechanisms of decision making, focusing on individual cognitive and affective factors and their influences on information processing, decisional satisfaction, regret and quality of life. Guided by a self-regulation theoretical framework, Dr. Diefenbach translates and applies basic psychological phenomena into applied patient focused interventions with the goal of enhancing decision making and ultimately quality of life for patients. Dr. Diefenbach's research has been continuously federally funded for more than 15 years and has involved a variety of patient populations, including prostate and breast cancer patients. In an effort to enhance patient decision making he has developed in-person as well as web-based programs. His Prostate-Interactive Education System (PIES) was one of the first web-based comprehensive and interactive prostate cancer information resources for newly diagnosed prostate cancer patients. In addition, he guided the development of three additional programs: Healing Choices for Prostate Cancer and Healing Choices for Breast Cancer, as well as a web-based resource for prostate cancer survivors (PROGRESS). More recently, Dr. Diefenbach developed applications for the smart phone to support a slow-breathing exercise to control vasomotor symptoms experienced by men on androgen deprivation therapy (2Breathe) and a cancer screening information tool (HealthOwl).

Research Interests:

  • Patient treatment decisions under distressing and uncertain medical conditions
  • The development of in-person, web-based, and smartphone programs focusing on the patient as well as the partner/caregiver
  • Investigating the basic psychological mechanisms of decision making, focusing on individual cognitive and affective factors and their influences on information processing, decisional satisfaction, regret and quality of life
  • Risk communication and shared decision making
  • Quality of life


Research focus:

Clinical intervention trials

1R01 CA158019-01 (PI: Miller, S, Ph.D.) 06/01/2011-05/31/2016
Role: PI for NSLIJ subcontract 
RCT of an online multimedia program to boost coping and function for PCA survivors
This project proposes to develop and evaluate an online resource for prostate cancer survivors.

1 R01-CA118682-01 (PI: Diefenbach, M.A.) 08/1/2007 – 07/31/2012
The Functions of Affect in Treatment Decisions of Rising PSA Patients
This longitudinal study examines the role affect plays in treatment or watchful waiting decisions among prostate cancer survivors, who experience a rising PSA.

PC101223 (PI: Diefenbach, M.A, Ph.D) 07/15/2011-7/14/2014
An Intervention to control vasomotor symptoms for advanced prostate cancer patients on hormone therapy
This project develops and evaluates a brief, portable paced respiration breathing exercise using the iPod Touch platform to control vasomotor symptosm experienced by patients on hormone treatment.

1R211CA155963 (PI: Diefenbach, M.A., Ph.D) 07/14/2011-12/31/2014
Brief Intervention to Improve Quality of Life & Couple Functioning after Prostate Surgery 
Project evaluates the feasibility and acceptability of a brief couples-focused intervention targeting prostate cancer patients and their partners.

R34DE022273 (PI: Badr, H., Ph.D) 09/15/2011-08/31/2014 
Role: Co-Investigator 
Improving Oral Health and Quality of Life After Oral Cancer: A Web-based Approach 
This study proposes a web-based intervention, called Computer Assisted oral health REhabilitation and Support (CARES), which is guided by Self Determination Theory (SDT). Specific aims are: 1a) To develop and evaluate the content of the CARES intervention; 1b) To evaluate the feasibility of the CARES prototype; and 2) To pilot test the initial efficacy of CARES.

1R21 (Diefenbach, M.A, Ph.D) 09/01/2012-08/31/2014 
Decision making for active surveillance in prostate cancer patients and spouses
The project aims to investigate the decision making process for AS using a theory-guided self-regulation approach focusing on cognitive, affective and social/spousal factors.

P01-CA057586-09A2 (PI: Marcus, A) 09/1/2006-8/30/2012 
Project Leader for Project 1: Preparatory interventions for prostate cancer. 
This study, part of a program project, develops and evaluates a multimedia web-based education and decision system for prostate cancer patients to be used with the Cancer Information Service.


University of Wisconsin-Madison

Degree: MS

Rutgers - The State University of New Jersey

Degree: Doctorate

Institute for Health, Health Care Policy and Aging

Degree: Post-Doctoral Training

Fox Chase Cancer Center in Philadelphia

Degree: First Faculty Appointment