A key difference to remember is that tantrums usually have a purpose. The person who is "acting out" in the moment is looking for a certain reaction from you (e.g., to push YOUR anger button in order to piss you off). On the other hand, a meltdown is a reaction to something that short circuits the reasoning part of the brain (e.g., sensory overload, anxiety overload, unexpected and troubling change in the person's routine or structure, feeling overwhelmed by one's emotions, etc.), and has nothing to do with your response to it.
ASD is often referred to as the "invisible disorder" because of the internal struggles these individuals have without outwardly demonstrating any real noticeable symptoms (when they are calm anyway). People with this disorder struggle with a stressful problem, but “internalize” their feelings until their emotions boil over, leading to a complete meltdown. These outbursts are not a typical tantrum.
Some meltdowns are worse than others, but all leave both spouses exhausted. Unlike tantrums, meltdowns can last anywhere from ten minutes to over a day – or more. When it ends, both partners are emotionally drained. But, don’t breathe a sigh of relief yet. At the least provocation, for the remainder of that day, and sometimes into the next, the meltdown can return full force.
Meltdowns are overwhelming emotions and quite common in people on the spectrum. They can be caused by a very minor incident to something more traumatic. They last until the individual with ASD is either completely exhausted, or he gains control of his emotions (which is not easy for him to do). Most autistics have “emotional-regulation” difficulties!
Your spouse with ASD may experience both minor and major meltdowns over incidents that are part of daily life. He may have a major meltdown over something that you view as a very small incident, or he may have absolutely NO REACTION to something that you view as a very troubling incident.
When your husband is calm and relaxed, talk to him about his meltdowns. Then, tell him that sometimes he “reacts” to (i.e., is startled by) certain problems in a way that is disproportionate to the actual severity of the problem. Have him talk to you about a sign you can give him to let him know when he is starting to get revved-up. Overwhelming emotions are part of the traits associated with the disorder, but if you work with your spouse, he will eventually learn to control them somewhat (try to catch them in the “escalation phase” rather than after that bomb has already ignited).
People with ASD usually like to be left alone to cope with negative emotions. If your husband says something like, “I just want to be left alone,” respect his wishes for at least a while. You can always go back in 30 minutes and ask if you can help. Do not be hurt if he refuses.
Resources for couples affected by ASD: