For the first time, researchers from the Queensland Brain Institute have proven that a mild stress is enough to trigger post-traumatic stress disorder (PTSD) in mouse models of autism spectrum disorder (ASD).
Dr Shaam Al Abed and Dr Nathalie Dehorter have demonstrated that the two disorders share a reciprocal relationship, identifying a predisposition to PTSD in ASD, and discovering that core autism traits are worsened when traumatic memories are formed.
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 Al Abed.
ASD and PTSD share common features, including impaired emotional regulation, altered explicit memory, and difficulties with fear conditioning.
“We demonstrated in four mouse models of ASD that a single mild stress can form a traumatic memory.”
“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 Dehorter, dysfunction in the prefrontal cortex has been linked to both disorders.
“We identified specific cortical circuit alterations that trigger the switch between the formation of a normal memory and a PTSD-like memory during stress,” said Dr Dehorter.
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 over activation of the prefrontal cortex that is present in ASD and throws out the balance of these cortical circuits.
The capabilities of interneurons to respond to stress is altered in ASD. This alteration worsens autism traits following the formation of a traumatic memory.
“We didn’t anticipate that forming a traumatic memory would aggravate the social and behavioural difficulties in ASD.”
“What is really promising is once the traumatic memories are successfully recontextualised using behavioural therapy, the ASD traits that were worsened following the stress, are dramatically improved.”
This discovery validates the assumption that the two disorders are closely linked and could change the way clinicians treat their patients.
An awareness of the PTSD predisposition and the success of behavioural therapy in treating it could shape the approach to managing stress in ASD.
This paper was published in iScience.