A recent study in Psychiatry Research: Neuroimaging sheds new light on the brain’s role in rumination, a mental pattern often linked to depression. Researchers found that people who tend to ruminate have structural differences in a region of the brain called the precuneus, which seems closely tied to other brain areas involved in memory, self-focus, and attention. These findings suggest that rumination in depression may stem from how various brain networks interact rather than isolated brain regions.
Depression can vary widely in its effects, but many people with depression experience rumination—repetitive, self-focused thoughts on negative experiences, which can worsen the condition. Since previous research linked certain brain regions with depression-related symptoms, this study aimed to clarify which brain areas might be specifically associated with rumination. Understanding these relationships could help develop more targeted treatments for depression, particularly for individuals who experience severe or prolonged rumination.
“Most people are probably familiar with rumination. It’s where you get stuck, so to speak, continually thinking about the same thoughts, most often about unhappy memories or situations,” said study author Niall W. Duncan, an associate professor at Taipei Medical University’s Institute of Mind, Brain and Consciousness. “This type of negative thinking is a common symptom of depression, so understanding why this happens is important. If we can understand what causes people to have these repetitive thought patterns then hopefully we can find ways to help them stop.”
The researchers collected data from a group of individuals with major depressive disorder (32 participants) and compared it with a group of healthy controls (69 participants). To ensure that brain structure differences were accurately captured, all participants underwent detailed brain scans using structural magnetic resonance imaging (MRI), which produces high-resolution images of brain structures, particularly the grey matter. Grey matter consists mainly of neurons and is often associated with various cognitive functions, including memory, perception, and self-reflection. Additionally, participants completed a questionnaire assessing rumination tendencies, providing a quantifiable measure of how much they focused on repetitive, negative thoughts.
The analysis involved comparing the grey matter volume in both groups to identify any differences associated with depression. More specifically, the study used surface-based, whole-brain analysis to examine grey matter across the entire cortex, focusing on cortical surface area and thickness. This approach allowed researchers to see if there were regions in the brain where people with depression showed different structural patterns compared to the control group. The key areas of interest included brain regions previously associated with self-referential thinking and executive function, as these cognitive processes are thought to play a role in rumination.
The study’s findings were somewhat unexpected. While the researchers observed that individuals with depression had increased grey matter volume in the dorsolateral prefrontal cortex, this area did not show a connection to rumination.
“Going into the research, we expected to see differences in the grey matter in the lateral frontal brain and that this change in grey matter would be linked to the rumination people reported,” Duncan told PsyPost. “We did see the grey matter changes expected but these were not linked to the rumination. Instead, it was a region in the back of the brain that was connected to the rumination. This was unexpected but made more sense when we looked at how these different parts of the brain are connected with each other.”
Rumination was found to correlate with structural properties in the right precuneus, which is part of the default mode network, a set of interconnected brain regions active when people are introspective, imagining, or processing memories. The analysis showed that participants who reported higher levels of rumination tended to have a lower surface area in the right precuneus, suggesting that this brain area might play a specific role in fostering the repetitive thought patterns associated with rumination.
To further explore this link, the researchers conducted a functional connectivity analysis using data from an independent sample of 100 individuals. This analysis revealed that the precuneus is highly connected with other brain networks involved in executive function, autobiographical memory, and visual processing. This connectivity pattern includes links to the dorsolateral prefrontal cortex, indicating that structural changes in one area (such as the precuneus) may influence other connected regions.
The implication here is that rumination may result from a network-level interaction, where specific structural changes in the precuneus have downstream effects on related brain areas, leading to repetitive self-reflective thought patterns. This supports a broader theory that depression symptoms may emerge not from isolated regions in the brain but from the ways different brain regions interact as networks.
“Our findings fit in with a general shift in how we think about the brain,” Duncan explained. “It has been common to think of the brain as having specific regions that do one specific thing – the idea of a region ‘for’ something. While there is truth to this, it is probably better to think of the brain as a complete system where all the parts need to work together.”
“What we see is that the rumination symptoms in the people we studied appear to be connected to one part of the brain that is well connected to lots of other ones. This might mean that the symptoms come from the system as a whole being put out of balance. That’s a tentative conclusion though that needs more investigation.”
But the study, like all research, includes some caveats.
“It’s important to note that the people we were looking at were all older and had had depression for quite a long time,” Duncan explained. “They were also almost all taking medication for their depression. These factors mean that what we found might not apply to people who have only recently developed depression. It may also be the case that what we observe is a consequence of the medication that people are taking, rather than of the depression directly. Finally, our participant group was relatively small so we’d definitely want to see the results replicated in other, larger, samples.”
Future studies might explore how rumination-related brain networks develop over time and whether early intervention could prevent structural brain changes in those with depression.
“We continue to look at the processes in the brain that are connected to rumination,” Duncan said. “This is the current main focus of the co-leader of the research, Dr Tsu-Yu Hsu. She is working on how rumination may be linked to differences in how people process mental contents that are related to themselves. This would make sense, since rumination is generally an issue where people have repetitive self-related thoughts.”
The study, “Structural alterations in a rumination-related network in patients with major depressive disorder,” was authored by Paul Z. Cheng, Hsin-Chien Lee, Timothy J. Lane, Tzu-Yu Hsu, and Niall W. Duncan.
