Brain networks associated with repetitive thoughts: concerns for teenagers 💭

A study describes for the first time the brain networks associated with mental rumination, these repetitive thoughts, and their evolution between the ages of 18 and 22.

This work, conducted by the Inserm team "Developmental trajectories in psychiatry" (Inserm/ENS Paris-Saclay) at the Borelli Center for Applied Mathematics[1], also shows a connection between the brain networks of rumination and certain psychiatric symptoms.


The researchers relied on the IMAGEN cohort aimed at exploring the mental health of young Europeans starting at age 14. This work, published in the journal Molecular Psychiatry, provides avenues for mental health prevention.

Rumination refers to repetitive thoughts, with the feeling of going in circles. It often manifests during the transition from adolescence to young adulthood and is notably linked to the challenges of entering adult life.

The literature describes three types of rumination. "Reflective" rumination is not negative; it aims to find a solution to a problem and can be part of a thought process (finding housing, employment, etc.). "Worrisome" rumination is related to complex or conflictual situations, with difficulties in taking a step back (professional concerns, financial hardships, etc.). Finally, the third type of rumination is "depressive" in nature, characterized by repetitive dark thoughts about one's situation or future.

Common among teenagers, this last type can be associated with states of anxiety, aggression, depression, or even addictions. As a recognized risk factor for psychiatric disorders, it often precedes the onset of disorders in adulthood. This is why it is important to better understand the brain mechanisms associated with it.

With this goal in mind, a team led by Inserm researchers Jean-Luc Martinot and Eric Artiges, at the laboratory "Developmental trajectories in psychiatry", focused for the first time on the brain networks associated with different types of rumination during the transition from adolescence to young adulthood.

To this end, the team studied 595 young individuals included in the European IMAGEN cohort[2] and followed them between the ages of 18 and 22.

Specific networks associated with rumination

The participants underwent resting-state fMRIs. This neuroimaging technique allows scientists to track spontaneous brain activity in all regions of the brain.

"During this examination, the participants were given no specific instructions and were left free to their own thoughts. As a result, the 'ruminator' profiles naturally fell into their ruminations," explains Jean-Luc Martinot.

These young individuals also completed questionnaires to measure the frequency and type of their ruminations, as well as to assess the potential presence of psychiatric symptoms.

Firstly, the researchers cross-referenced the imaging data with the questionnaire responses at age 18, using an innovative mathematical model. This allowed them to associate each type of rumination with the simultaneous activity of two to three specific brain networks.

For example, they showed that at age 18, "worrisome" ruminations were supported by brain networks involving the hippocampus and the frontal lobe. "Depressive" ruminations, on the other hand, were associated with other networks involving the thalamic nucleus and part of the frontal lobe.

Changes at age 22

This study was then repeated with the same participants at the age of 22 to assess how the rumination patterns and associated brain processes evolved over time.

"At this stage of life, young adults showed a decrease in 'worrisome' ruminations in favor of 'reflective' ruminations," explains Jean-Luc Martinot, "suggesting that between the ages of 18 and 22, a period of transition into adulthood, they have developed better emotional adaptation skills and better decision-making abilities."

This is reflected on a neurological level: by transitioning from one type of rumination to another, the researchers observed that the brain networks activated in the participants were also reshaped.

In the next phase of the study, the team further demonstrated that the brain networks associated with different types of rumination were also linked to certain psychiatric symptoms. Specifically, the activity of a network associated with "worrisome" rumination was also related to "internalized" symptoms (anxiety, nervousness, withdrawal, etc.). The activity of a network associated with "depressive" rumination was also tied to "externalized" symptoms (agitation, irritability, acting out, substance abuse, etc.).

"This work reveals connections between the evolution of mental ruminations and the evolution of psychiatric symptoms, through functional changes in the brain at the end of adolescence. Two types of rumination may precede psychiatric symptoms. These findings could contribute to the development of preventive approaches for young adults," concludes Jean-Luc Martinot.

Notes:

[1] The Borelli Center is under the supervision of CNRS/ENS Paris-Saclay/Université Paris-Saclay/Université Paris-Cité/Inserm/Military Health Service.

[2] Co-founded by Jean-Luc Martinot, the IMAGEN cohort is designed to track the mental health of adolescents starting at age 14, using psychological, clinical, environmental, and brain imaging data.