Depression may lead to dementia--study

Rebecca Wood, chief executive of the Alzheimer's Research Trust, said, "Similarities in symptoms between dementia and depression can mean the two are sometimes confused at time of diagnosis, but we don't know if they are biologically linked.

"These latest studies suggest that there may be profound connections between dementia and depression so we must expand the research to find out more."

Study to assess the link between depression and dementia
In a bid to determine whether depression actually paves the way for dementia, the researchers examined 949 people who took part in the Framingham Heart Study.

The average age of the participants was 79 years and none of them exhibited any obvious signs of mental impairment. For the purpose of the study, the subjects were questioned about general depression, sleep complaints, social relationships and also monitored for signs of any mental disorder.

The analysis revealed that 125 adults were suffering from depression at the onset of the study. All the volunteers were then tracked for a period of 17 years.

Dr. Jane Saczynski of the University of Massachusetts, who led the study stated, “We have such long follow-up in our study, it lends support to depression as a risk factor for dementia and not merely a consequence.

Outcome of the study
At the close of the study, 164 participants were suffering from dementia, while 136 people were diagnosed with Alzheimer's disease.

The researchers noted that nearly 22 percent of the subjects who were depressed at the onset of the study developed dementia as opposed to 17 percent who were free from stress.

Dr. Jane Saczynski of the University of Massachusetts, who led the study stated, “We have such long follow-up in our study, it lends support to depression as a risk factor for dementia and not merely a consequence.

“Everyone wants to find risk factors for dementia and know what increases risk. Here we identify one more risk factor.”

Some plausible explanations
Though the link between depression and dementia is ambiguous, the scientists believe certain factors may contribute to mental decline.

Experts theorize that the brain tissue of stressed out people can become inflamed, which might put one at risk of dementia.

In addition, certain proteins in the brain that increase with depression may also influence the risk of developing dementia.

Moreover, lack of physical exercise, isolation, poor diet, smoking, certain lifestyle factors and underlying health issues could play a vital role in developing the degenerative disease.

Dr. Yonas Geda of the Mayo Clinic states, "The association between late-life depression and cognitive impairment does not appear to be spurious.

“However, there is insufficient evidence at present to support the hypothesis that depression has a direct causal relationship with subsequent dementia. Only a future mechanism of disease study with a biologic marker for depression can clearly identify which of the ... hypotheses is most pertinent.”

The study was supported by the National Institute on Aging, the National Institute of Neurological Disorders and Stroke, and the National Heart Lung and Blood Institute

The findings of the report have been published in the journal 'Neurology.'