Early research on PDA was carried out by Elizabeth Newson and colleagues and published through conference proceedings and informal channels.
The research literature remains small at present. However, interest is growing, and PDA is beginning to attract international attention.
Recent work has led to some helpful developments:
Development of ways to quantify PDA features – The ‘Extreme Demand Avoidance Questionnaire’ (EDA-Q, p. 31 of this booklet) was developed to quantify PDA features based on parent report, with the aim of identifying individuals at high risk of exhibiting the PDA profile for research purposes (O’Nions et al., 2014). More recently, work has been undertaken in collaboration with Dr. Judith Gould to revisit existing items within the Diagnostic Interview for Social and Communication Disorders (DISCO). The aim was to identify which items appear most specific to PDA, compared to the rest of the autism spectrum. This analysis identified eleven DISCO items that appear very distinctive to the PDA profile (O’Nions et al., 2015). More information is available in the research paper, which is available open access and can be downloaded from the European Child and Adolescent Psychiatry website.
PDA features are dimensional within the autism spectrum - Two recent studies have compared individuals with PDA to those with more classic presentations of ASD, using informant questionnaires and interviews. Both reported similar levels of autistic traits and core features of ASD in those with and without PDA features (O’Nions et al., 2013; 2015). The findings also suggest that PDA traits are continuously distributed in individuals on the spectrum. Those with substantial PDA features also appear to span a range in terms of the severity of their autistic features. In short, PDA features should be considered dimensional (O’Nions et al., 2015).
Substantial PDA features are associated with difficult behaviours and anxiety - Those with the highest levels of PDA features have significantly higher levels of socially maladaptive and difficult behaviours, plus high levels of anxiety/emotional symptoms, compared to those without (O’Nions et al., 2013, O’Nions et al., 2015).
Better understanding of the clinical presentation of PDA in an adult inpatient setting (Eaton & Banting, 2012), and in children with epilepsy (Reilly et al., 2014) – These case studies provide insight into the usefulness of incorporating description of PDA features in a diagnostic formulation. In particular, Eaton & Banting highlight the challenges of managing an individual with PDA, and identifying triggers of extreme behaviour. They also describe barriers to implementing the recommended strategies.
Insight into the prevalence and stability of PDA - Other work using the DISCO to quantify PDA features has provided insight into the prevalence and stability of this profile in individuals on the autism spectrum (Gillberg et al., 2015). Estimates of prevalence vary depending on the precise criteria used, but this study reported that one in five of those with ASD may have some features, with one in twenty-five of those with ASD exhibiting the more narrowly defined phenotype. The study focused specifically on individuals identified as having ASD, and as such, acknowledges that the prevalence may be under-estimated.
Insight into the educational experiences of individuals with PDA (Gore-Langton et al., 2015) – This work has shown that children with PDA display a range of hard to manage behaviours at school, and require high levels of additional support. They also experience high rates of exclusion and educational placement breakdown across a range of specialist and mainstream school settings. For more information see http://pdaeducationalexperiences.wordpress.com.
Self-report version of the Extreme Demand Avoidance Questionnaire - Dr Vincent Egan, Associate Professor of Forensic Psychology at the University of Nottingham gave a presentation on his research work into adults with PDA at the NAS PDA Conference in November 2015. The research is looking at whether the EDA-Q can be used to measure PDA features in adults using a self-report method.
More research is needed, particularly in the following areas:
- Studies that systematically examine whether individuals identifi ed as having PDA features meet diagnostic thresholds for ASD.
- Further validation of tools to quantify PDA features.
- Investigation of the cognitive profi le in PDA would shed light on how much individuals with PDA have in common with those with more classic presentations of ASD, and whether the presence of behaviours associated with ASD (e.g. socially inappropriate and obsessive behaviour) has a similar or distinct underlying cognitive basis.
- Studies examining which educational and management strategies are most useful for individuals with PDA.
Post-doctoral Fellow at the Parenting and Special Education Research Unit, KU Leuven,