depression memory

Three types of depression identified

October 31, 2018

Science Daily/Okinawa Institute of Science and Technology (OIST) Graduate University

Scientists have used brain imaging to identify three sub-types of depression -- including one that is unresponsive to commonly prescribed serotonin boosting drugs.

 

According to the World Health Organization, nearly 300 million people worldwide suffer from depression and these rates are on the rise. Yet, doctors and scientists have a poor understanding of what causes this debilitating condition and for some who experience it, medicines don't help.

 

Scientists from the Neural Computational Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), in collaboration with their colleagues at Nara Institute of Science and Technology and clinicians at Hiroshima University, have for the first time identified three sub-types of depression. They found that one out of these sub-types seems to be untreatable by Selective Serotonin Reuptake Inhibitors (SSRIs), the most commonly prescribed medicines for the condition. The study was published in the journal Scientific Reports.

 

Serotonin is a neurotransmitter that influences our moods, interactions with other people, sleep patterns and memory. SSRIs are thought to take effect by boosting the levels of serotonin in the brain. However, these drugs do not have the same effect on everyone, and in some people, depression does not improve even after taking them. "It has always been speculated that different types of depression exist, and they influence the effectiveness of the drug. But there has been no consensus," says Prof. Kenji Doya.

 

For the study, the scientists collected clinical, biological, and life history data from 134 individuals -- half of whom were newly diagnosed with depression and the other half who had no depression diagnosis- using questionnaires and blood tests. Participants were asked about their sleep patterns, whether or not they had stressful issues, or other mental health conditions.

 

Researchers also scanned participants' brains using magnetic resonance imaging (MRI) to map brain activity patterns in different regions. The technique they used allowed them to examine 78 regions covering the entire brain, to identify how its activities in different regions are correlated. "This is the first study to identify depression sub-types from life history and MRI data," says Prof. Doya.

 

With over 3000 measurable features, including whether or not participants had experienced trauma, the scientists were faced with the dilemma of finding a way to analyze such a large data set accurately. "The major challenge in this study was to develop a statistical tool that could extract relevant information for clustering similar subjects together," says Dr. Tomoki Tokuda, a statistician and the lead author of the study. He therefore designed a novel statistical method that would help detect multiple ways of data clustering and the features responsible for it. Using this method, the researchers identified a group of closely-placed data clusters, which consisted of measurable features essential for accessing mental health of an individual. Three out of the five data clusters were found to represent different sub-types of depression.

 

The three distinct sub-types of depression were characterized by two main factors: functional connectivity patterns synchronized between different regions of the brain and childhood trauma experience. They found that the brain's functional connectivity in regions that involved the angular gyrus -- a brain region associated with processing language and numbers, spatial cognition, attention, and other aspects of cognition -- played a large role in determining whether SSRIs were effective in treating depression.

 

Patients with increased functional connectivity between the brain's different regions who had also experienced childhood trauma had a sub-type of depression that is unresponsive to treatment by SSRIs drugs, the researchers found. On the other hand, the other two subtypes -- where the participants' brains did not show increased connectivity among its different regions or where participants had not experienced childhood trauma -- tended to respond positively to treatments using SSRIs drugs.

 

This study not only identifies sub-types of depression for the first time, but also identifies some underlying factors and points to the need to explore new treatment techniques. "It provides scientists studying neurobiological aspects of depression a promising direction in which to pursue their research," says Prof. Doya. In time, he and his research team hope that these results will help psychiatrists and therapists improve diagnoses and treat their patients more effectively.

https://www.sciencedaily.com/releases/2018/10/181031093337.htm

Depression linked to memory problems and brain aging

May 9, 2018

Science Daily/American Academy of Neurology

Depression in older adults may be linked to memory problems, according to new research. The study also showed that older people with greater symptoms of depression may have structural differences in the brain compared to people without symptoms.

 

"Since symptoms of depression can be treated, it may be possible that treatment may also reduce thinking and memory problems," said study author Adina Zeki Al Hazzouri, PhD, MS, of the University of Miami Miller School of Medicine in Florida. "With as many as 25 percent of older adults experiencing symptoms of depression, it's important to better understand the relationship between depression and memory problems."

 

The study involved 1,111 people who were all stroke-free with an average age of 71. The majority were Caribbean Hispanic. At the beginning of the study, all had brain scans, a psychological exam and assessments for memory and thinking skills. Their memory and thinking skills were tested again an average of five years later.

 

At the start of the study, 22 percent of participants had greater symptoms of depression. This was defined as a score of 16 or higher on a test with a range of 0-60, which is considered at risk for clinical depression. For the test, participants reported how often in the past week they agreed with statements such as "I was bothered by things that usually don't bother me" and "I did not feel like eating." Researchers found after adjusting for age, race, anti-depressive medications, and other variables, greater symptoms of depression were linked to worse episodic memory. Scores on tests were lower by 0.21 of a standard deviation compared to those without greater symptoms of depression. Episodic memory is a person's ability to remember specific experiences and events.

 

Researchers also found those with greater symptoms of depression had differences in the brain including smaller brain volume as well as a 55 percent greater chance of small vascular lesions in the brain.

 

Researchers found no evidence of a relationship between greater symptoms of depression and changes in thinking skills over five years.

 

"Small vascular lesions in the brain are markers of small vessel disease, a condition in which the walls in the small blood vessels are damaged," said Zeki Al Hazzouri. "Our research suggests that depression and brain aging may occur simultaneously, and greater symptoms of depression may affect brain health through small vessel disease."

 

Zeki Al Hazzouri noted that the study provides information about depression and memory and thinking skills, especially among people who identified as Hispanic, who have been insufficiently studied in previous studies on the topic, even though they can be at increased risk of dementia in late life.

 

Limitations of the study include that participants had to be healthy enough to have an MRI, so they may have been healthier than the general population. Also, the study was over a five-year period, which may not have been long enough to capture meaningful changes in thinking and memory abilities over time.

https://www.sciencedaily.com/releases/2018/05/180509162704.htm

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