Brains of teens with depression remain on high alert to social rejection

Adolescent girls with major depressive disorder show atypical brain responses when anticipating social rejection, failing to adapt to repeated threats over time. These patterns suggest that depression alters social learning on a neurological level, keeping the brain on high alert in challenging peer interactions. The findings were published in the Journal of Affective Disorders.

Adolescence is a sensitive period for social and emotional development. During these teenage years, interactions with peers become intensely important. The brain is actively learning how to navigate social environments, categorizing experiences as safe or threatening.

A specific brain structure involved in this process is the amygdala, an almond-shaped cluster of neurons deep within the temporal lobe. The amygdala helps detect emotionally salient information and potential threats in the environment.

When a person is repeatedly exposed to the same emotional stimulus, the amygdala usually adapts and its activation decreases. This process is called habituation. Habituation is a fundamental mechanism of learning that allows the brain to conserve energy when a situation becomes predictable.

In youth who suffer from major depressive disorder, neural responses to social feedback often differ from those of healthy teenagers. Michele Morningstar, a psychologist at Queen’s University, and her colleagues conducted a study to explore how depression influences the brain’s ability to learn from repeated social threats. They focused specifically on whether the amygdala successfully habituates to the anticipation of being rejected by a peer.

The researchers recruited seventy-six girls between the ages of 10 and 17. The sample was divided into three categories based on clinical interviews. Twenty-two participants were diagnosed with major depressive disorder. Thirty participants had a familial risk for the condition, meaning they had a parent with a history of depression, but they had no personal diagnosis. The remaining twenty-four girls served as a low-risk control group, having neither a personal diagnosis nor a family history of depression.

To observe the participants’ brains in action, the researchers used functional magnetic resonance imaging. This technology tracks blood flow in the brain to measure neural activity in real-time. While inside the scanner, the girls participated in a specialized behavioral experiment called the Chatroom Interact task.

Before the scan, the participants were asked to view profiles of other teenagers and select several individuals they would be interested in talking to online. During the scanning session, they were told they were connected to a virtual chatroom with two of these chosen peers. In reality, the peers were simulated profiles controlled by the researchers.

The task required the participants to take turns being chosen for discussions about various teenage topics, such as books, music, or friends. For each round, the virtual peers would supposedly choose someone to talk to. The researchers programmed one virtual peer to act in a “mean” manner, rejecting the participant 67 percent of the time. The other virtual peer was programmed to be “nice,” accepting the participant 67 percent of the time.

The experiment included sixty trials, allowing the participants ample opportunity to learn the behavioral patterns of the two virtual peers. The researchers specifically focused their analysis on the anticipation period of the task, the window of time when the participant was waiting to see the virtual peer’s decision. The team measured how the amygdala responded during these periods to see if brain activity changed as the girls gradually learned which peer was exclusionary.

In the low-risk and at-risk groups, the amygdala showed signs of habituation. As the trials progressed and the mean peer’s behavior became highly predictable, activation in both the left and right sides of the amygdala steadily declined. The brains of these girls learned the pattern and stopped reacting as strongly to the anticipated threat.

The girls diagnosed with major depressive disorder exhibited a different pattern. Their right amygdala showed a flatter response across the trials, failing to habituate to the anticipation of the rejecting peer’s decision. Their brains continued to react as if the social threat was new and unpredictable, maintaining a steady level of high activation.

To test if this failure to habituate was specific to social threats, the team conducted a secondary analysis focusing on the trials involving the nice peer. The amygdala did show habituation when anticipating the friendly peer’s choices. This pattern did not differ across the three groups. The sustained high alert observed in the depressed youth was unique to facing potential rejection.

The researchers also conducted an analysis to examine other brain areas involved in processing threats and rewards, including the anterior insula and the subgenual anterior cingulate cortex. The anterior insula habituated to the mean peer across all participants, and there were no differences between the depression groups.

The at-risk girls did show higher overall activation in the subgenual anterior cingulate cortex compared to the healthy controls. However, the rate of change over time in this region was similar across all groups. The specific failure to adapt to repeated social threats was localized to the right amygdala in the group with an active depression diagnosis.

These patterns suggest that teenagers experiencing depression might struggle to update their expectations based on past social interactions. An amygdala that cannot habituate to social threats could lead to constant emotional exhaustion and heightened vigilance. This might encourage withdrawal from social situations, potentially worsening depressive symptoms over time.

While the results offer a window into adolescent brain development, the sample was restricted to girls. Because the incidence of depression increases dramatically in teenage girls, focusing on this demographic is highly relevant for public health. Still, the results cannot reliably be generalized to other gender identities or to adult populations. The researchers noted that additional studies are needed to determine if these neurological patterns hold true for boys or adults with depression.

The study also relied on implicit learning, measured purely by tracking brain activity. The researchers did not test whether the participants explicitly realized which peer was the rejecting one. Future research could measure whether this neural habituation directly affects how teenagers consciously evaluate their peers or modify their actual behavior in real-world social environments.

Investigating these neural dynamics on a larger scale could reveal how individual differences, such as baseline anxiety, influence social learning. Exploring the connections between the amygdala and other regions might also provide a more comprehensive map of how depression alters the processing of negative social feedback.

The study, “Reduced amygdala habituation to anticipated social rejection in youth with major depressive disorder,” was authored by M. Morningstar, M.N.K. Gravelle, D.P. Dickstein, J.S. Silk, R.E. Dahl, E.E. Nelson, D. Yee, and L.R. Stroud.