A new research has found that people diagnosed with depression experience decline in their ability to think sharply. They found that bipolar disorders are part of a mood disorder spectrum. Published in the journal BRAIN, the research showed that women who were depressed or bipolar exhibited different activity levels in their right posterior parietal cortices than those whose mental health was fine.

This part of the brain plays a vital role in performing executive functions like reasoning, working memory and problem solving.

"These findings support the idea of seeing mood disorders dimensionally, as a continuum of function to dysfunction across illnesses that are more alike than distinct", said Kelly Ryan, Ph. D., lead author for the study.

For the study, the researchers gave detailed tests to 612 women. Of them, 66% were diagnosed with either depression or bipolar disorder. The researchers decided to conduct the study only on women to avoid gender differences that may complicate results.

The researchers received funding for the study from the National Institute of Mental Health, the National Alliance for Research on Schizophrenia and Depression, the University of Michigan Department of Psychiatry Research Committee and fMRI lab, the Richard Tam Foundation and the U-M Depression Center's Heinz C. Prechter Biopar Research Fund.

Researchers are of the belief that the study findings have opened doors for making it better to diagnose and effectively treat patients with these disorders.

The bipolar patients showed increased brain activity when in a non-depressed state. But they showed increased brain activity in region called the dorsolateral prefrontal cortex, which is responsible for actively regulating emotions.

In a depressed state, bipolar patients showed low brain activity in the rostral anterior cingulate cortex. This region plays a role of a hub connecting the cognitive and emotional parts of the brain.