How Do Positive and Negative Experiences Shape PTSD Development After Trauma?

What you need to know

• Brain responses to rewards and punishments shortly after trauma predict PTSD symptoms a year later
• Heightened amygdala response to punishments predicts more severe PTSD, especially hyperarousal and intrusion symptoms
• Reduced ventral striatum response to rewards predicts more severe PTSD, especially avoidance symptoms
• Early changes in risk-taking behavior after trauma may influence PTSD development
• Findings suggest targeting both negative and positive emotional processing could help prevent chronic PTSD

The brain’s response to rewards and punishments after trauma

When someone experiences a traumatic event, how their brain processes positive and negative experiences in the aftermath may influence whether they develop post-traumatic stress disorder (PTSD). A new study used brain imaging to examine how trauma survivors respond to rewards and punishments in the weeks following trauma, and how this relates to PTSD symptoms over the following year.

The researchers looked at two key brain systems:

1. The negative valence system, centered on the amygdala, which processes threats and punishments.

2. The positive valence system, centered on the ventral striatum, which processes rewards and positive experiences.

They found that how these systems function shortly after trauma can predict who is more likely to develop severe PTSD symptoms later on.

Heightened threat response linked to worse PTSD

The study involved 171 trauma survivors who underwent brain scans about one month after experiencing a traumatic event, such as a car accident. While in the scanner, participants played a gambling game where they could make risky or safe choices to win points.

The researchers examined how participants’ brains responded when they received punishments (losing points) versus rewards (winning points) in the game. They found that trauma survivors who showed a stronger amygdala response to punishments were more likely to have severe PTSD symptoms both initially and one year later.

Specifically, heightened amygdala activity was linked to more severe hyperarousal symptoms (like being easily startled or always on guard) and intrusion symptoms (like flashbacks or nightmares). This suggests that an overactive threat detection system in the brain may contribute to the development of these PTSD symptoms over time.

Blunted reward response also predicts PTSD

While much PTSD research has focused on threat processing, this study also found that blunted responses to rewards play an important role. Trauma survivors who showed reduced activity in the ventral striatum when receiving rewards were more likely to have severe PTSD symptoms one year later, especially avoidance symptoms.

The ventral striatum is involved in motivation and reward processing. A dampened response in this region may reflect reduced ability to feel pleasure or motivation after trauma, potentially leading to withdrawal and avoidance behaviors characteristic of PTSD.

Interestingly, reduced connectivity between the ventral striatum and a region called the ventromedial prefrontal cortex during reward processing also predicted worse PTSD symptoms later on. This brain circuit is important for valuing rewards and making decisions. Disrupted functioning of this circuit may impair trauma survivors’ ability to properly evaluate positive experiences.

Changes in risk-taking behavior may influence PTSD trajectory

In addition to brain activity, the researchers also looked at participants’ behavior in the gambling game. They found that trauma survivors who showed decreased willingness to make risky choices in the game shortly after trauma tended to have more severe PTSD symptoms at that time.

This behavioral shift towards safer choices was particularly associated with more severe avoidance and intrusion symptoms initially. The researchers suggest this may reflect an overactive threat detection system (leading to more avoidance) combined with reduced reward sensitivity.

Intriguingly, the study found that changes in risk-taking behavior over time influenced the relationship between early brain responses and later PTSD symptoms. Trauma survivors who became even less willing to take risks over the first 6 months and also had heightened amygdala threat responses initially were most likely to develop severe PTSD by one year.

This suggests that both initial brain responses and ongoing behavioral changes work together to shape the trajectory of PTSD development. Becoming overly risk-averse after trauma may compound the effects of an overactive threat detection system in the brain.

Implications for PTSD prevention and treatment

The findings highlight the importance of considering both negative and positive valence processing in understanding PTSD. While much research has focused on fear and threat, this study suggests that impaired reward processing and motivation also play a crucial role, particularly in the development of avoidance symptoms.

The researchers used an advanced machine learning technique to rank the importance of different brain measures in predicting PTSD. Surprisingly, they found that measures of reward processing (ventral striatum activity and connectivity) were actually more important than threat processing (amygdala activity) in predicting who would develop severe PTSD symptoms.

This suggests that treatments aimed at preventing chronic PTSD may benefit from targeting both heightened threat sensitivity and blunted reward sensitivity early after trauma. Potential approaches could include:

• Cognitive-behavioral techniques to modulate exaggerated threat responses
• Behavioral activation strategies to increase engagement with positive activities
• Mindfulness practices to enhance awareness of positive experiences
• Cognitive restructuring to address overly negative interpretations of events

The study also highlights how changes in behavior, like becoming overly cautious, can influence PTSD trajectories. Helping trauma survivors maintain a balanced approach to risk and reward may be beneficial. This could involve gradually confronting feared situations while also encouraging engagement in enjoyable activities.

Conclusions

• Both heightened brain responses to threats and blunted responses to rewards shortly after trauma predict worse PTSD symptoms later on
• Impaired reward processing may be especially important in the development of avoidance symptoms
• Changes in risk-taking behavior after trauma can compound the effects of altered brain responses
• Early interventions for PTSD may benefit from targeting both threat and reward processing
• Maintaining engagement with positive experiences after trauma could help prevent chronic PTSD

While more research is needed, this study provides important insights into the brain mechanisms that may contribute to PTSD development after trauma. The findings suggest that a balanced approach addressing both negative and positive valence processing could enhance efforts to prevent and treat PTSD.