Some autistic meltdowns look a lot like toddler tantrums from the outside — and if you encounter a young child on the spectrum having one, you may even think they're simply throwing a tantrum. The two phenomena are by no means the same thing, however, and anyone who regularly has contact with an autistic person or autistic people should understand the difference.
What are temper tantrums, and what causes them?
Stanford Children's Health describes a temper tantrum as "a way a young child lets out strong emotions before he or she is able to express them in socially acceptable ways". This seems pretty accurate to me.
Toddlers, who are at an age where they're developing all sorts of opinions and wishes as they realize they're a whole separate person of their own, still lack the language and developmental skills to describe those opinions and wishes verbally and calmly. They may tantrum when they're having a hard time making a transition, when they want something they can't have, when they're tired and overwhelmed, when you take something they want away from them, when they're "hangry" (angry because they're hungry), when they don't understand what you want, when they feel you're treating them unfairly, and so on.
Make no mistake — though some toddler tantrums "just happen", toddlers have absolutely been known to engage in this kind of behavior on purpose, by choice, as evidenced by the fact that some stop very quickly when they get that ice cream or their parents agree to let them watch one more Peppa Pig episode.
I've never heard anyone use the term "temper tantrum" to describe anything except this kind of toddler rage-trip, unless the person was joking or seeking to belittle someone else's behavior.
What are autistic meltdowns, and what causes them?
One autistic adult describing different "levels" of meltdowns told me that they may simply be overwhelmed during mild meltdown — emotionally and with sensory overload — and be overtaken by a flow of uncomfortable emotions internally. They may lose their ability to speak, the person said, and to listen to what others are saying, but don't externalize what is happening. A more severe meltdown may feature anger and yelling, while the most intense meltdowns cause screaming and outright aggression over which the person doesn't have any control.
Not all meltdowns are outwardly aggressive, however. To cope, a person may also sit down on the floor, engage in intense "stimming" (such as rocking, repeating phrases, flapping hands, and many more), or physically exit the situation as fast as possible. These are also sometimes called "shutdowns" instead.
Autistic people of all ages can experience meltdowns, though not all do, and these meltdowns do not, in any way, reflect their functioning outside of the meltdowns.
What do temper tantrums and autistic meltdowns have in common? How are they different?
Though some people will appreciate it if you stay with them and act as a source of comfort in previously agreed-on ways during a meltdown, others will need time on their own. Someone on the spectrum having a meltdown will never benefit from being told to calm down in a condescending way, being told to get it together, or from any kind of aggressive behavior. They need to get away from triggering circumstances, and adding to them will only make it worse.
An autistic meltdown is not the same as a panic attack — to which it's sometimes compared — either, but these two phenomena may have more in common than meltdows and tantrums. In both cases, the person temporarily loses control of their emotions and actions. An autistic meltdown may, in some ways, share even more similarities with an asthma attack — both are more likely upon exposure to identifiable triggers, both are totally beyond the control of the person experiencing them, and steps can be taken to cope with both.