On the subject of "meltdowns" and why an autism diagnosis is so helpful. (See also National Autistic Society)
Meltdowns are Not temper tantrums.
Let me repeat that, because it is So important to understand: Meltdowns are Not temper tantrums.
But they look like temper tantrums, right?
Sure they fucking do (to begin with). And an autistic child is equally capable of either. And that's a clue as to why, without a diagnosis, without going on a journey of understanding, without becoming connected to other parents who "get it"; who can share often near identical experiences, it is so hard to tell.
But think on this: how often does a neuro-typical kid have temper tantrums, and at what ages?
Terrible twos? Becoming less beyond that? From perhaps frequent, to weeks, months apart, maybe never, once a kid has started school? As a child learns more about themselves and how they fit into the social environment, they learn the norms of behaviour and adapt to them. Yay!
Meltdowns are Not temper tantrums.
Meltdowns happen when an autistic person is so overwhelmed that they lose behavioural control. And you can't and mustn't try to handle them like temper tantrums.
But Why are they overwhelmed?
Well, that's a whole other topic.
But for now consider the "spoon theory", i.e. we all have say 12 spoons of energy/power to do tasks in a day, including basic things like brushing teeth, which for me might take up just 1 spoon, or probably a fraction of a spoon.
A neurotypical person might get through the day and use up all their spoons, or not, or maybe they extend themselves a bit and end up running on empty, or shattered. But maybe a Mars bar or a coffee and, hey, we got ouselves a spoon extension...
An autistic, however, may find that brushing their teeth takes up 2 spoons. The sensory triggers alone - something in their mouth, sensation of brushing, taste of toothpaste - could be abhorrent to them (sensory trigger), let alone the anxiety caused by knowing they have to do this task soon, and how that anxiety may ramp up in the moments (minutes, hours even) in the build up to it (anxiety trigger).
As an analogy, think how you might feel having to strip naked and get into a bath full of tarantulas for 3 minutes twice a day.
If you hate spiders (your sensory trigger), you might see how this repetitive twice daily task might do your fucking swede in, huh? It might cause anxiety, mental fatigue, and much more.
Each autistic person is different, and has a unique set of triggers. But most go through the day encountering many triggers that quickly use up all their spoons. Those triggers are often sensory, but very hard to spot or understand are the many triggers in seemingly ordinary social interactions, and places like Schools double down with extra demands for them to focus on cognitive tasks and learning.
As a parent, once you understand that meltdowns are Not temper tantrums, you can start tracking back from meltdowns to what were the triggers, and how to avoid them (the tarantulas!) or manage them (brushing teeth).
We're still looking for the right toothpaste, by the way :-)