Similarities found in the brains of hibernating black bears and humans with major depressive disorder may inform understanding of major depressive disorder in humans

Staten Island, N.Y. – April 28, 2023 - The New York State Office for People With Developmental Disabilities (OPWDD) today announced the publication of a study by researchers from its Institute for Basic Research in Developmental Disabilities (IBR) that finds similarities in the levels of a signaling molecule in the brains of black bears during hibernation and in humans experiencing major depressive disorder (MDD).

Metabolic depression is an adaptation that helps black bears survive the winter season by severely reducing the amount of energy their body generates. Black bears are used to study human depression because the neurobiological changes associated with their hibernation are similar to changes that occur in humans with MDD.

The IBR study, published in the article, “Downregulation of cyclic adenosine monophosphate levels in leukocytes of hibernating captive black bears is similar to reported cyclic adenosine monophosphate findings in major depressive disorder,“ in Frontiers in Psychiatry, examined levels of the molecule cyclic adenosine monophosphate (cAMP) in captive female black bears. cAMP is a cellular signal occurring within cells, that is important in many biological processes. The study found that cAMP levels were much lower during the hibernation state than in the pre-hibernation and exit-from-hibernation states. This finding suggests that changes in the bears’ cAMP levels depend on the state of the bear’s metabolism, much like the changes associated in humans with varying states of severity of MDD. The association of changes in cAMP levels with the state of the organism disputes the theory that cAMP dysfunction is the cause of MDD, which has been suggested recently. This study is the first to document changes in cAMP levels during mammalian hibernation.

“This intriguing study offers important understanding of the changes involved in major depressive disorder,” said Dr. Jill Pettinger, OPWDD Deputy Commissioner of Statewide Services. “This new insight of the neurobiology of major depressive disorder and its similarities to hibernation has the potential to guide further research that may eventually help inform development of improved treatments.”

The study team, led by John A. Tsiouris, MD, psychiatrist at IBR’s George A. Jervis Clinic, and clinical associate professor in the Department of Psychiatry, New York State Downstate Medical Center, measured cAMP concentrations in blood specimens collected from captive black bears by researchers at Virginia Polytechnic Institute and State University and sent the samples to IBR for analysis. Michael Flory, Ph.D., head of IBR’s Research Design and Analysis Service, conducted statistical analyses for the study.

The IBR researchers recommend further studies to confirm their theory that a form of lowered metabolism produced by the suppression of the mitochondria, as seen in captive black bears, underlies the process responsible for MDD in humans. Viewing MDD as an old adaptive process for survival could lead to new areas of research into the cause and neurobiology of this disorder.

About OPWDD and IBR:

The Institute for Basic Research in Developmental Disabilities (IBR) is the research arm of the New York State Office for People With Developmental Disabilities (OPWDD). IBR also provides clinical services and conducts educational programs. OPWDD is responsible for coordinating services for New Yorkers with developmental disabilities, including intellectual disabilities, cerebral palsy, Down syndrome, autism spectrum disorders, Prader-Willi syndrome, and other neurological impairments.