Across our nationwide portfolio of addiction treatment centers, we offer a network of industry experts who will oversee your recovery journey as you work toward sobriety. Because we know how important your loved one is to you, and that building trust is essential, we wanted to showcase some of our facility leadership team.

Read more about our Chief Medical Officer and National Medical Director for Clinical Diagnostics as well as our medical directors at each facility.

AAC’s Corporate Leadership

Dr. Lawrence Weinstein, Chief Medical Officer

dr-Lawrence-WeinsteinIn August of 2018, Dr. Lawrence Weinstein was appointed Chief Medical Officer at American Addiction Centers (AAC). He has over 20 years of experience in managed behavioral healthcare, including private practice where he provided addiction psychiatry, family therapy, and individual and group diagnostic psychotherapeutic services.

His research on how the brain affects the immune system (psychoneuroimmunology) and the connection the brain has to the body, confirmed his belief in mind-body connection, enhancing his desire to address the whole person when it comes to treatment.

Throughout his career, Dr. Weinstein has been a force for driving technology solutions that support clinical innovation and has set the standard for clinical and operational excellence. As chief medical officer, he offers an unwavering commitment to patient care, oversees medical operations for all facilities and supervises the medical staff to ensure the highest quality of care.

Dr. Mark Calarco, National Medical Director for Clinical Diagnostics

dr-Mark-CalarcoDr. Mark Calarco was appointed national medical director for clinical diagnostics at AAC in August of 2018. Previously, he served 5 years as the chief medical director at AAC before continuing his work with our Addiction Labs to develop innovative products and services in order to yield better treatment outcomes for patients. With over 25 years of experience in the industry, including family and emergency medicine, Dr. Calarco is a thought leader in addiction science and an established researcher.

Although the catalyst of Dr. Calarco’s career started with the tragic loss of his brother due to a medical mistake, this tragedy inspired his passion for helping others and his interest in health care. Dr. Calarco’s commitment to serving those in need and to clinical excellence impacts the lives of many people each day.

AAC Facility Medical Directors

Dr. Casey Green, Greenhouse Treatment Center

dr-Casey-GreenDr. Casey Green serves as the medical director of Greenhouse Treatment Center in Grand Prairie, Texas. He received his B.A. in biology from the University of Texas in Austin and earned his medical degree from the University of Texas in Galveston. Raised in the Dallas-Fort Worth area, Dr. Green has worked in the addiction treatment industry for more than a decade in the Lone Star State.

Dr. Green has a wide range of experience in managing medically- and psychiatrically-complex patients throughout the treatment process. Through his own personal journey with sobriety and via specialized training, Dr. Green understands how to effectively blend medicine and psychiatric care in addiction treatment.

“Greenhouse Treatment Center is at the forefront of addiction treatment with its focus on clinical excellence, implementation of new technology, commitment to research and innovative treatment plans,” says Dr. Green.

Dr. Paul Little, Laguna Treatment Center

dr-Paul_LittleIn 2014, Dr. Paul Little joined AAC and currently serves as the medical director at Laguna Treatment Hospital in Aliso Viejo, California. Prior to his role, he worked as a medical director at Acadia Healthcare for 5 years. He brings over 20 years of experience to his role, with the majority of his time practicing addiction medicine.

Dr. Little’s interest in addiction medicine was piqued when he returned to West Virginia after serving as a doctor in the U.S. Air Force and began working for a consortium of rural health clinics in the hills of Appalachia. During this time, he witnessed many loggers and miners struggle with opioid addiction in order to handle the chronic pain from their injuries. He was one of the first pioneers to create a Suboxone clinic in the area to help with the epidemic. In 2009, this medication-assisted program (MAT) earned him a community recognition award from the governor of West Virginia.

Dr. Little has led a MAT program at a standalone outpatient clinic, San Diego Addiction Treatment Center, and pushed for family to be involved in the treatment of addiction. Having had firsthand experience with addiction within his own family, he understands the importance of family support in the recovery process. When he’s not practicing medicine, he’s biking, reading novels, and spending time with his family.

Dr. Richard Seely, Recovery First

dr-richard-seelyDr. Richard Seely serves as the medical director at Recovery First located in Hollywood, Florida. He brings nearly 40 years to AAC as a practicing psychiatrist within his position as a medical director. Dr. Seely received his medical degree from Sidney Kimmel Medical College at Jefferson University and completed his residency at Thomas Jefferson University Hospital.


Dr. Stephen Pannel, Oxford Treatment Center

dr-stephen-pannelCertified by the American Board of Addiction Medicine, board certified in adult psychiatry, and specializing in dual-diagnosis issues, Dr. Stephen Pannel, DO, ABPN, ABAM, is a medical director at Oxford Treatment Center’s withdrawal management program in Etta, Mississippi. He completed his residency in psychiatry at the University of Arkansas for Medical Sciences and went on to complete a fellowship in child and adolescent psychiatry at the University of Alabama at Birmingham. Dr. Pannel believes that it’s possible to prevent a lifelong pathway to mental illness by opening the door to early intervention within young people.


Dr. Michael Coburn, AdCare Rhode Island

dr-michael-coburnDr. Michael Coburn is a medical director at AdCare in North Kingstown, Rhode Island. Previously, he was a medical director for a methadone maintenance treatment program for 5 years. Dr. Coburn graduated from the Dartmouth-Brown Program in Medicine in 1988, completed his surgical residency in 1995, and is board certified in addiction medicine.


Dr. Mohammed Alhabbal, AdCare Massachusetts

Dr. Mohammad AlhabbalCertified by the American Academy of Family Physicians and the American Board of Addiction Medicine, Dr. Mohammed Alhabbal, ABFP, ABAM is the medical director at AdCare Hospital in Worcester, Massachusetts.

Dr. Alhabbal completed his Family Medicine Residency at the University of Massachusetts Medical School. He is currently serving as the assistant professor in the Department of Family Medicine’s Hospitalist Division at the same university. He’s held a number of positions at AdCare for over a decade.

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