The DSM is the American Psychiatric Association's manual of mental health diagnoses, setting out the criteria clinicians use to decide whether a diagnosis such as ADHD or autism fits.
The current edition is DSM-5-TR, a text revision published in 2022. It sets out the criteria for ADHD and autism spectrum disorder, including how many traits need to be present, from what age and in how many settings.
In Ireland and the UK, clinicians also use ICD-11, the World Health Organization's classification. The interviews we use, DIVA-5 for ADHD and ADI-R for autism, are mapped to both, in line with NICE guidelines.
The DSM describes patterns that clinicians agree on. It is written by people and revised as research changes. Before 2013, autism was split into several diagnoses. Now it is one. It's a useful shared language, not a description of who you are.