How the condition develops in the elderly is still largely unknown

Nov 9, 2011 09:55 GMT  ·  By
PET scans show higher FDDNP binding (yellow areas) and thus more abnormal proteins in a patient with major depressive disorder compared with a healthy control
   PET scans show higher FDDNP binding (yellow areas) and thus more abnormal proteins in a patient with major depressive disorder compared with a healthy control

Even though major depressive disorder (MDD) is one of the most widespread conditions among seniors, scientists are still at a loss in explaining how the diseases develops. In a new study, experts use a unique brain scan technique to observe the development of the condition in seniors' brains.

What researchers at the University of California in Los Angeles (UCLA) were especially interested in was the underlying biology of MDD development in seniors. They therefore focused their effort on quantifying levels of amyloid plaques and tau tangles in test subjects' brains.

Both amyloid and tau proteins have been linked to the development of Alzheimer's disease, a neurodegenerative form of dementia. The fact that they may play a role in the development of MDD as well intrigued investigators, who began searching for a connection between the two.

Details of the new investigation were published in the latest issue of the peer-reviewed, scientific journal Archives of General Psychiatry. Amyloid plaques and tau tangles were until now thought to be related exclusively to memory loss present in dementias.

However, some researchers suggested a while back that their presence may also be linked to the emergence of certain symptoms related to mild depression and anxiety. The link was only proposed for older adults and seniors.

The type of positron emission tomography (PET) brain scan the UCLA team applied to observe this potential connection was augmented by the use of the chemical marker FDDNP. The molecule binds to plaques and tangles, revealing them in their entirety during the scans.

By using this approach, the team was able to determine the exact locations in the senior brains where these proteins were accumulating. The posterior cingulate cortex and lateral temporal areas were discovered to be the main targets of the proteins.

Both these areas are involved in advanced cognitive functions, including decision-making, complex reasoning, memory and emotions. “This is the first study using FDDNP to assess the abnormal protein levels in brains of older adults with severe depression,” Dr. Gary Small says.

The expert – who holds an appointment as the UCLA Parlow-Solomon Professor on Aging – was the senior author of the study. He is also a professor of psychiatry with the Semel Institute for Neuroscience and Human Behavior at the university.

“The findings suggest that the higher protein load in critical brain regions may contribute to the development of severe depression in late life,” the investigators goes on to say.

“We may find that depression in the elderly may be an initial manifestation of progressive neurodegenerative disease,” proposes Dr. Anand Kumar, the first author of the new research effort.

He holds an appointment as the Lizzie Gilman Professor and department head of psychiatry at the University of Illinois in 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,” the expert concludes.