> For the complete documentation index, see [llms.txt](https://docs.ixdx.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ixdx.org/clinical-background/a-brief-history.md).

# A brief history

The 3di was initially developed as a research tool starting around 1998 at the Great Ormond Street Institute of Child Health under the direction of Professor David Skuse. The World Health Organisation's *International Statistical Classification of Diseases and Related Health Problems, 10th revision*, or ICD-10, came into effect in 1993. Meanwhile the American Psychiatric Association's *Diagnostic and Statistical Manual of Mental Disorders, fourth edition*, or DSM-IV, was published in 1994. The 3di treated the two systems as broadly equivalent, and the 3di's first ASD assessment was built around an amalgamation of ICD-10 and DSM-IV criteria.

The first autism assessment in the 3di, now known as the *ICD-10 extended*, contained 134 questions, and was designed for research use where there was sufficient time for such a thorough assessment.

Over the following years, demand grew for a quicker autism informant interview for use in CAMHS clinics where there was less time available. This led to the development of the *ICD-10 brief* assessment.

DSM-5 came into effect in 2013, followed by ICD-11 in 2022. The 3di was updated with a new *DSM-5 extended* assessment for autism in 2013. Finally in late 2022 the *DSM-5 brief* assessment was released.

Comparing DSM-5 and ICD-11, we consider that by design the two sets of criteria are so similar that ASD outcomes (and many others) can be reported as DSM-5 or as ICD-11. The 3di always references DSM-5 because the APA got there many years before the WHO; you can substitute one term for the other in your reports or perhaps reference neither.