How Do Life Stressors and Brain Responses to Rewards Affect Depression Risk in Adolescent Girls?

What you need to know

• Experiencing more acute life stressors over one’s lifetime predicts increases in depression symptoms in adolescent girls, but only for those who show blunted brain responses to rewards.
• A stronger brain response to rewards may protect against the depressive effects of acute life stress exposure.
• The findings suggest that enhancing reward responsiveness could potentially increase resilience to stress and reduce depression risk in adolescents.

How life stress and brain reward responses affect depression risk

Depression is a common and serious mental health condition that often begins during adolescence, especially for girls. Researchers have identified two key factors that seem to play a role in depression risk: experiencing stressful life events, and showing reduced brain responses to rewards. However, much of the previous research has looked at these factors separately or focused only on recent stressors. This study aimed to examine how lifetime exposure to stressful events might interact with brain responses to rewards to predict increases in depression symptoms over time in adolescent girls.

Measuring stress exposure and reward responses

The researchers recruited 245 adolescent girls aged 8-14 years old and followed them over a two-year period. At the start of the study, the girls completed a simple computer task where they could win small amounts of money while their brain activity was recorded using electroencephalography (EEG). This allowed the researchers to measure each participant’s neural response to rewards, specifically looking at a brain signal called the reward positivity (RewP). The RewP reflects how strongly the brain responds to receiving a reward versus not receiving a reward.

Two years later, the girls completed a comprehensive assessment of stressful life events they had experienced over their lifetime using a tool called the Stress and Adversity Inventory for Adolescents (Adolescent STRAIN). This measures both acute stressors (short-term events lasting a few days, like getting into an accident) and chronic stressors (long-lasting difficulties of at least one month, like ongoing financial problems). The participants also completed questionnaires about their depression symptoms at both time points.

Acute stress exposure interacts with reward responses

The key finding was that greater exposure to acute stressors over one’s lifetime predicted increases in depression symptoms two years later, but only for girls who showed a blunted reward positivity response at the start of the study. In other words, experiencing more acute stressful events was linked to worsening depression, but this effect was strongest in those whose brains responded less strongly to rewards.

Interestingly, this interaction was not found for chronic stressors. While chronic stress exposure did predict increases in depression symptoms overall, this effect did not depend on individual differences in reward responsiveness.

Understanding the brain-behavior link

These results fit with a “diathesis-stress” model of depression, which proposes that some individuals have pre-existing vulnerabilities that make them more susceptible to developing depression when exposed to stressful life events. In this case, blunted reward processing in the brain appears to be a vulnerability factor that increases risk for depression in the face of acute stress exposure.

But why might reduced reward responsiveness make someone more vulnerable to stress-induced depression? One possibility is that people who respond less strongly to rewards may be less likely to seek out or engage in rewarding activities that could help buffer against the negative effects of stress. They may also have more difficulty maintaining a positive outlook or motivating themselves to cope with stressors.

On the flip side, having a stronger neural response to rewards seems to be protective, even for those who experience high levels of acute stress. This suggests that interventions aimed at enhancing reward responsiveness could potentially increase resilience and reduce depression risk in adolescents exposed to stressful life events.

Implications for understanding and treating depression

These findings have several important implications:

1. They highlight the importance of considering both environmental factors (like stress exposure) and individual differences in brain function when trying to understand depression risk.

2. They suggest that acute, short-term stressors may be particularly impactful for depression risk in adolescents, especially for those with blunted reward processing.

3. They point to reward responsiveness as a potential target for interventions aimed at preventing or treating depression. For example, behavioral activation therapy, which encourages engagement in rewarding activities, might be especially helpful for individuals with blunted reward responses.

4. They underscore the value of taking a lifespan perspective when studying depression risk factors, rather than focusing only on recent events.

Limitations and future directions

It’s important to note some limitations of this study. The sample consisted only of adolescent girls, so it’s unclear if the same patterns would be found in boys or adults. The participants were also primarily from white, middle-class backgrounds, so more diverse samples are needed to ensure these findings generalize to other populations.

Additionally, while the study followed participants over two years, it would be valuable to track people for even longer periods to see how these risk factors play out over time. Future research could also examine whether interventions that enhance reward responsiveness might actually prevent depression in high-risk adolescents exposed to acute stressors.

Conclusions

• Experiencing more acute stressful life events predicts increases in depression symptoms for adolescent girls, but primarily for those who show blunted brain responses to rewards.
• A robust neural response to rewards may serve as a protective factor against stress-induced depression.
• Interventions aimed at enhancing reward responsiveness could potentially increase resilience to stress and reduce depression risk in vulnerable adolescents.

This study provides valuable insights into how life experiences and brain function interact to shape depression risk during the crucial developmental period of adolescence. By identifying specific risk factors and potential protective mechanisms, this research paves the way for more targeted and effective approaches to preventing and treating depression in young people.