Why negative beliefs may be harder to shift in PTSD

Negative beliefs about safety, trust and the consequences of trauma are considered a core part of post-traumatic stress disorder (PTSD). They can contribute to a continuing sense of threat and are associated with more severe PTSD symptoms.

A new study explored why these beliefs may be difficult to revise. The researchers focused on brain communication during cognitive restructuring, a technique used in cognitive behavioural therapy to help people examine unhelpful beliefs and consider evidence that may challenge them.

What the researchers tested

Agathos and colleagues studied 70 adults with PTSD and 66 trauma-exposed controls recruited from the community in Melbourne, Australia. Participants underwent 7-Tesla functional MRI after cognitive restructuring training.

During the task, participants viewed 16 negative self-referential statements. They selected eight statements to challenge using cognitive restructuring strategies and silently repeated the other eight. They rated how strongly they endorsed each statement before and after the task.

The researchers first used general linear model analyses to identify brain regions that were more active while participants challenged, rather than repeated, negative thoughts. They then used dynamic causal modelling to estimate the direction and strength of communication among a predefined group of regions, including the mediodorsal thalamus, medial prefrontal cortex and other regulatory areas.

Both groups reduced endorsement during the task

Before the task, the PTSD group endorsed the negative statements more strongly than the trauma-exposed control group. The average endorsement score was 4.88 in the PTSD group, compared with 2.81 among controls.

Both groups gave lower endorsement ratings after challenging the statements. However, the size of this immediate reduction did not differ meaningfully between the groups.

That result shows that participants could change their ratings in the context of the experiment. It does not show that the underlying beliefs changed permanently, or that cognitive restructuring works equally well in everyday life or during therapy.

A difference in brain communication

The brain analyses pointed to dynamic, reciprocal activity in a thalamocortical network involving regions linked with self-referential thinking and cognitive control.

The researchers found weaker inhibitory modulation of the mediodorsal thalamus by the medial prefrontal cortex in participants with PTSD than in trauma-exposed controls. The authors suggest that this weaker influence could allow negative information to remain more accessible to conscious awareness, potentially making it harder for disconfirming information to update existing beliefs.

They also propose that the medial prefrontal cortex may help reduce the self-relevant value assigned to a negative belief when challenging information is considered. In this account, weaker communication with the mediodorsal thalamus could make it more difficult for that belief to move out of conscious focus.

Within the PTSD group, stronger modulation was associated with less severe negative beliefs about the world and other people. It was not associated with beliefs about the self or self-blame. The association may relate to social cognition and threat appraisal, although the researchers noted that it could also reflect the types of trauma experienced by participants, many of whom had experienced interpersonal trauma.

What the study cannot show

The findings do not establish that altered communication between the medial prefrontal cortex and mediodorsal thalamus causes persistent negative beliefs. They also do not show that changing this pathway would improve PTSD treatment outcomes.

The brain measure did not reliably predict whether an individual had a PTSD diagnosis. The study was cross-sectional, so it could not determine whether the observed differences preceded trauma exposure, developed after trauma, or emerged alongside PTSD.

The sample also limits how broadly the findings can be applied. Almost 93% of the PTSD group and about 76% of the control group were female. Most participants in the PTSD group had a co-occurring mood or anxiety disorder, and nearly three-quarters were taking psychiatric medication. The study did not investigate the possible effects of those factors.

Participants were recruited from one community in Melbourne, and a high proportion had experienced interpersonal or abuse-related trauma. The statements used in the task reflected PTSD-related descriptions but were not tied to each participant’s own traumatic experiences. The modelling also examined only a predefined and limited brain network.

Why the findings matter

Cognitive restructuring is designed to help people reach their own conclusions by examining evidence, rather than simply replacing one belief with an alternative interpretation. Understanding the brain processes involved could eventually help researchers explain why negative beliefs are more resistant to change for some people with PTSD.

For now, the study identifies a possible neural mechanism and a direction for future research, not a treatment target ready for clinical use. The authors called for longitudinal and intervention studies with more representative samples, balanced sex distributions, and closer assessment of different trauma types and psychiatric conditions.

The same general questions may also be relevant to anxiety and depressive disorders, where negative cognitions are important features and cognitive restructuring is used. But this study did not test whether its findings apply to those conditions.

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