People with autism appear predisposed to PTSD

Researchers from The Australian National University (ANU) and The University of Queensland (UQ) have demonstrated that autism spectrum disorder (ASD) and post-traumatic stress disorder (PTSD) share a reciprocal relationship, identifying a predisposition to PTSD in ASD and discovering that core autism traits are worsened when traumatic memories are formed. Their research has been published in the journal iScience.

ASD and PTSD share common features, including impaired emotional regulation, altered explicit memory and difficulties with fear conditioning. But while recent studies in humans have highlighted the co-occurrence of ASD and PTSD, the link between the disorders is often overlooked and remains poorly understood.

“We set out to determine the occurrence of traumatic stress in ASD, and to understand the neurobiological mechanisms underlying the reported predisposition to PTSD,” said Dr Shaam Al Abed, from UQ and ANU.

“We demonstrated in four mouse models of ASD that a single mild stress [event] can form a traumatic memory,” she continued. “In a control population, on the other hand, PTSD is triggered by extreme stress. We wanted to understand this unique perception of stress in ASD that leads to the formation of PTSD.”

The prefrontal cortex is a highly specialised area in the front part of the brain that plays a crucial role in social cognition and behaviour. According to Dr Nathalie Dehorter, also from UQ and ANU, dysfunction in the prefrontal cortex has been linked to both disorders.

“We were able to show the specific brain circuit alteration that’s underlying the hypersensitivity to stress in ASD,” she said. We know what’s happening at the cellular and at the structural level in the prefrontal cortex.”

The prefrontal cortex contains specialised cells called interneurons, which are crucial for adapted fear memorisation and normal sensory function and play a key role in stress-related disorders. The formation of PTSD-like memories is triggered by overactivation of the prefrontal cortex that is present in ASD and throws out the balance of these cortical circuits.

“We identified specific cortical circuit alterations that trigger the switch between the formation of a normal memory and a PTSD-like memory during stress,” Dehorter said.

The capabilities of interneurons to respond to stress is altered in ASD. To the researchers’ surprise, this alteration worsened some of the core traits of autism, such as repetitive behaviour, following the formation of a traumatic memory.

“Understanding this hypersensitivity is crucial to treating those traumatic memories with the right behavioural therapy,” Al Abed said. “By recontextualising the traumatic memory, we can hopefully alleviate the worsening of those core traits.”

According to the researchers, the study supports the idea that everyday life situations — like entering a particularly noisy or unfamiliar environment — can be experienced as traumatic by neurodivergent populations. The study also calls for better awareness of PTSD in autism, to allow for efficient intervention for those more likely to experience trauma.

“Timely detection appears to be essential, especially if PTSD can worsen the core ASD traits,” Dehorter said.

“We need more research into the overlap between these two conditions.”

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