Adult autism assessment sits at the long end of an already stretched mental health queue, and how long the wait actually runs varies sharply depending on which provider the referral lands with. That variation is the part most people only discover months in, once the waiting has already started.
Plan for a year, sometimes more, and build that into your expectations early rather than being blindsided by it later. Adult autism (autismespectrumstoornis) diagnostics sit within specialized GGZ, which already runs past the Treeknorm for most people, and autism assessment specifically tends toward the longer end because it requires a fuller diagnostic process than most referrals. How long exactly varies a lot by region and by which instelling you land with — some GGZ organizations report noticeably shorter lists than others in the same catchment area, which is part of why it's worth calling around rather than accepting whatever your huisarts's default referral partner offers. Registering with two or three providers at once is allowed and genuinely useful here, since you can drop the slower lists once one comes through. Your insurer's wachtlijstbemiddeling line can also redirect you to a provider with capacity if your current wait exceeds the Treeknorm. A private, self-pay assessment is possible and faster, though autism diagnostics tend to be pricier and more involved than an ADHD assessment, since the process typically includes developmental history and sometimes input from family. If you already have a diagnosis or assessment from another country, bring it — it won't skip the queue automatically, but it does inform the Dutch clinician's process.