Why Your Brain "Overthinks" — The Neuroscience of Rumination

Given the stress of high school, many adolescents have difficulty "turning off" their thoughts. These people constantly replay conversations, worry about upcoming events, or think about minor mistakes they have made. This pattern of thinking is called ruminating. Ruminating is a learned behavior based on how the brain processes and stores information. However, ruminating has a major impact on an individual's overall mental health.

Ruminating is defined as repeatedly focusing on a problem to determine its cause(s) and/or whether there will be additional consequences. While going back over past experiences can sometimes be beneficial, ruminating is problematic because it is excessive and non-productive. Studies show that one of the primary brain networks involved in ruminating is called the Default Mode Network (DMN). The DMN is active when an individual is not actively engaged in the outside world (i.e., while daydreaming, etc.). Individuals who engage in ruminating excessively have brains that are overly engaged in the DMN, increasing their likelihood of cycling through negative thoughts. Moreover, the Prefrontal Cortex of a person with rumination, which is responsible for decision-making and regulating cognition, is unable to inhibit such maladaptive thinking. Consequently, the brain gets trapped in a vicious cycle of overthinking. These biological mechanisms explain why individuals who want to worry less cannot do so.

Ruminating is strongly associated with a variety of mental health issues, including depression and anxiety. For example, Nolen-Hoeksema (2000) reported that individuals who engage in ruminating behaviors were at increased risk of having longer-lasting and more severe episodes of depression. There are several reasons for this association. A primary reason is that ruminating strengthens neural connections related to feelings of sadness/negativity. Thus, instead of solving a problem, the individual continues to revisit the problem, mentally reinforcing neural connections that relate to feelings of sadness/negativity. Additionally, ruminating impairs cognitive performance. Like test anxiety, ruminating consumes working memory (the limited amount of processing capacity available to process information in the brain). Thus, due to working memory being occupied by repetitive thoughts, an individual has less ability to pay attention, solve problems, or retain new information. Therefore, it is common for students who are overthinking to report poor concentration in class and struggle to complete homework on time. Ultimately, the cyclical nature of rumination creates a self-reinforcing pattern in which negative thinking perpetuates emotional distress, which in turn fuels further rumination. Addressing this pattern early through targeted interventions, such as cognitive-behavioral strategies, is therefore essential for supporting both the mental health and academic success of affected individuals.