Biology of Depression Linked to Dementia

Severe depression has plaques and tangles similar to dementia

(RxWiki News) From a biological level, severe depression and dementia in older adults look remarkably similar, psychiatrists have found. A new brain scan technique can pinpoint where protein deposits are accumulating.

In a recent trial, researchers were able to assess the level of amyloid plaques and tau tangles -- a hallmark of Alzheimer's disease and certain other dementias -- in older adults with major depressive disorder.

"Don't delay in seeking treatment for depression."

Past studies have found that the plaques and tangles are not only linked to memory loss, but also anxiety and mild depression in middle-age and older patients.

Dr. Gary Small, lead researcher, University of California Los Angeles Parlow-Solomon Professor on Aging and a professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior at UCLA, said this marks the first study to use a created chemical marker called FDDNP that binds to plaque and tangle deposits, allowing for them to be viewed by PET scan. This allows researchers to see exactly where the abnormal protein deposits are accumulating.

He said that findings suggest a higher protein load in critical brain regions may contribute to the development of severe depression in later life.

During the study researchers compared the FDDNP brain scans of 20 adults between the ages of 60 and 82 who had been diagnosed with major depressive disorder against scans of 19 healthy patients of similar age, gender and education.

They discovered that in patients with major depressive disorder, FDDNP binding was significantly higher throughout the brain and in critical areas of the brain that involve decision making, complex reasoning, memory and emotions.

Investigators also observed that protein deposits in different regions of the brain were associated with different symptoms with some appearing to suffer only from depression, while others also were mildly cognitively impaired.

"We may find that depression in the elderly may be an initial manifestation of progressive neurodegenerative disease," said Dr. Anand Kumar, first study author, the Lizzie Gilman Professor and department head of psychiatry at the University of Illinois at Chicago. "Brain scans using FDDNP allow us to take a closer look at the different types of protein deposits and track them to see how clinical symptoms develop."

UCLA currently owns three U.S. patents on the FDDNP chemical marker. Small and Dr. Jorge R. Barrio, an author and professor of molecular and medical pharmacology at the David Geffen School of Medicine at UCLA, are among the inventors.

The research was published inthe November issue of journal Archives of General Psychiatry.

Review Date: 
November 10, 2011