Researchers are warning that inconsistent use of the terms 'neurodiversity' and 'neurodivergence' in mental health research could obscure important differences between diagnoses and make findings harder to interpret.
They also say using the terms without further specification could encourage 'one-size-fits-all' approaches in clinics, schools and workplaces that can overlook individual care and support needs.
A new paper published in JAMA Psychiatry reviewed 134 studies and found that the term 'neurodivergence' is being used inconsistently in relation to over a dozen different clinical diagnoses across the different studies.
These included neurodevelopmental disorders, such as autism, ADHD, and dyslexia, but also many other psychiatric diagnoses, like depression and anxiety, and neurological disorders. One in five studies used the term without referring to any specific clinical diagnosis at all and without defining it.
"Neuro-affirming language can promote inclusion and help us to understand shared systemic barriers," says lead author of the paper Dr Alessio Bellato from the University of Southampton.
"Terms like 'neurodiversity' and 'neurodivergence' can also be useful in research focused on identity and lived experience, when studying shared characteristics of specified conditions, or for people awaiting assessment.
"However, grouping different clinical profiles under broad umbrella terms - especially when such terms are not formally defined - risks obscuring possible unique patterns and mechanisms that may be critical for driving science forward."
Researchers also stress the importance of not using these terms interchangeably.
Neurodiversity refers to the natural variation in how people's brains function, think, learn and process information. Saying "a child with neurodiversity" or "a neurodiverse child" is incorrect because neurodiversity describes variation across people, not a characteristic of one person.
Neurodivergent, on the other hand, can be used to describe someone whose brain functioning differs from what is considered to be 'neurotypical'. However, it is not clear how this difference is defined or measured.
The terms have gained popularity in recent years, partly due to efforts to advocate for the rights and inclusion of autistic people and those with mental health conditions. But the rapid uptake has resulted in the terms being applied inconsistently, interchangeably and sometimes incorrectly.
To better understand how the terms were being used in mental health research, an international team led by the University of Southampton and including experts with lived experience of neurodevelopmental and/or mental health conditions from ADHD Europe, Autism-Europe, and ADDISS UK, analysed 134 studies encompassing over 151 thousand participants.
50 studies asked participants to self-identify as neurodivergent or neurodiverse rather than using a formal clinical diagnosis, potentially adding further ambiguity.
56 studies didn't provide a definition of the terms, while in some cases studies used definitions which were inaccurate (especially for neurodivergence).
Professor Samuele Cortese , NIHR Research Professor and senior author of the paper from the University of Southampton said: "For clinical studies, we would generally encourage clarifying which specific clinical diagnoses were included. For example, if a study aims to assess a characteristic that is associated with ADHD but not autism, but the study sample is defined as 'neurodivergent' without further specification, the study results may be difficult to interpret.
"Importantly, our study has implications not only for research, but also for the care provided to those in need. Language is important for communication between patients, clinicians and other stakeholders involved in the care of patients. However, if the same term - such as 'neurodivergence' - is interpreted differently, important misunderstandings may arise which could affect the care the patient receives."
