The short answer is… not that I am aware of. Research into PDA is in its infancy. It is often the way that clinicians and parents notice trends first and then the research catches up. Researchers are just trying to get PDA recognised as a legitimate profile of Autism.
In Australia, practitioners on the ground are at the forefront of recognising and identifying PDA and developing best models of practice to assist PDAers and their families.
The best hypothesis is that PDAers have highly sensitive neuroception. This is coming from Stephen Porge’s research into Polyvagal Theory and its notion of neuroception, that our nervous system subconsciously detects safety or threat. This hypothesis certainly fits with what I see in my PDAer, in the children I have worked with, and the reports I hear from families of PDAers. Unless a better alternative theory presents itself this is the one that I am going to run with.
A crash course in polyvagal theory:
Our autonomic nervous system is responsible for regulating our physiological and emotional responses to different situations.
Polyvagal theory suggests that the nervous system has 3 pathways of response when responding to different types of stressors.
The most advanced pathway, or newest from an evolutionary standpoint, is the ventral vagal system which supports social engagement and connection under the condition of safety. This is state our system needs to be in to be to learn and develop relationships.
The second pathway is the sympathetic nervous system which supports survival through mobilization (this is our fight or flight response). Which becomes activated by perceived threat. The body responds by increasing our heart rate and our breathing.
The oldest and most primitive pathway is our dorsal vagal system which supports survival by immobilising and shutting down (that is our freeze response). It is typically activated in response to extreme stress, life threat or trauma.
Neuroception is our nervous system’s instinctual surveillance system and it is constantly measuring if we are safe or if we are under threat.
If we are safe, we can access the parts of our brain that allow us to interact, communicate, form relationships, apply judgement, rationalise and think properly.
If we detect threat, our system goes into a fight, flight, freeze, fawn stress response. This is not a conscious choice, our thinking brain has been short circuited.
Often times with PDA we can see varying expressions. There is a more external expression where that parasympathetic pathway is the most dominant- fight/flight- so they might display increased aggression, verbal attacks, breaking things, running away. And then there is a more internalised expression where the dorsal vagal is more dominant- freeze/fawn- where they might go under the radar – these might be the kids that become selectively mute, that shut down or that comply out of fear and neglect their own needs.
PDA brains have highly sensitive neuroception. They have a pervasive drive for autonomy, a need for control, a need for safety. The behaviour that we see in our PDA kids is not purposeful, it is a neurological response that is out of their control. Their body and brain are literally responding as if their life depends on it.
Behaviour is just the tip of the ice-berg with many factors hidden from view. A child’s threshold or tolerance changes day to day and is dependent on a range of factors: Sleep, hunger, thirst, temperature, sickness, fatigue, environment, people around them, sensory input, the amount of structure, autonomy, pressure, expectations and demands.
These factors can have a cumulative effect across days, weeks, and months. They might be able to cope with something one day but have a complete meltdown the next. School might go fine for a year and then completely fall apart. They may look very competent at home but become completely disabled in other settings or vice versa.
My sense is that PDAers have the underlying skills but they just can’t access them because their brain is frequently in a stressed state (fight/flight/freeze/fawn). An example of this, when our son completed the ADOS he came out as having extremely poor expressive language skills because he barely communicated with the therapist. At home, when he is safe, he constantly initiates back and forth conversations. His communication skills are not actually the problem, the problem lies with a dysregulated nervous system that prevents access to the skills he has, and then as a flow on effect, prevents the opportunity to practice. No amount of practicing expressive language skills is going to help a dysregulated nervous system. We have to go further up-stream.
Our job as parents, clinicians and teachers is to create safe environments (and by safe environments I’m meaning the child’s perception of safety), where PDAers can emerge out of their threat response.
