Autism and neurodiversity are contested fields with many different theories and experiences vying to be accepted as definitive. Within that PDA seems to be currently the most disputed. Ten years ago when I got a diagnosis ("on the Autistic Spectrum currently functioning at the level of residual Asperger's Syndrome") there seemed be quite frequent discussions on the radio questioning whether Asperger's Syndrome actually existed or if it was just an excuse used by inadequate parents for the misbehaviour of their children.
This strikes me as similar to the current attitude to PDA in that PDA is recognised by some practitioners in some areas and dismissed by other practitioners in other areas. There is an added layer of complication in that some people who accept the existence of a condition dispute if it is part of the autistic constellation (I've used this term because I think it describes autism better than spectrum, which is often conceptualised as a 2D line going from "low functioning" to "high functioning"). Some autistic people argue that it is Rational Demand Avoidance, an assertion people who identify as having the condition strongly dispute.
So what exactly is PDA and how does it affect people? Essentially it's an inability to comply with demands. It's generally considered to be part of the autism constellation that varies from other presentations of autism in the degree to which the person affected is unable to meet everyday demands.
PDA people often use social strategies to avoid meeting demands, so they appear superficially not to have the social difficulties usually associated with autism. Most PDA people say the demand avoidance is driven by extreme anxiety, it’s not that they don't wish to do whatever is required its more that overwhelming anxiety drives them to avoid any demands.
This means that ways of interacting that are often thought to be helpful for autistic people, such as being very direct and having set rules and timetables, are unhelpful for PDA'ers.
My sense from thinking and reading about PDA and talking to people with the condition is that demands impinge on their sense of self. The sense of agency is so shaky that it can feel as though complying with a demand obliterates the self. The level of threat felt results in any means possible being used to avoid the demand.
Autistic people have a tendency to extremes. In relation to demands this means that some non-PDA autistic people are rule followers, happy in situations with clear rules they can adhere to. Others need to be given a reason for any demand, they will then evaluate if they think the demand is reasonable and only comply if they agree with it, such people are often rebels. Both of these extremes can lead to whistle-blowing.
For PDA people however any demand feels unpalatable. This is not a pleasant position to find oneself in and it is made all the more difficult if one is then blamed and punished for being uncooperative.
As with other forms of neurodivergence I think the best way to address PDA is to listen to people who identify as having the condition and learning together what works best to enable them to fulfil their potential. I'm very grateful to some such people I 'met' on Twitter for commenting on drafts of this article.