What is inertia?

Sometimes, when faced with a situation, autistic people can't find the best way to act or the correct response to give. Faced with such a situation, they may suddenly be unable to move or speak. It's not on purpose, and it's not because the person no longer knows they're there. They understand what's going on, but are unable to act at that moment.

Inertia occurs when an autistic person is overloaded, causing confusion. The autistic person in a state of inertia will no longer be able to move. It’s not that the person can’t move, it’s that they can’t decide which movement to make. This may sound like one of the stress responses known as fight flight freeze. But that’s not quite the case.

Inertia in social situations

Autistic people have their own way of interpreting social interactions. Autistic people all have a way of communicating that is different from neurotypicals. Over time, some autistic people come to understand the way allistic (non-autistic) people communicate.

To communicate more effectively, many autistic people learn to prepare the words and actions they can use in social situations well in advance. Often, people in this situation will hesitate between several phrases or actions when it’s time to use them. If they can’t find the way to communicate that will give the desired result, they may fall into inertia. In other words, they don’t speak or move. It’s worse if the autistic person knows that there will be negative consequences if they don’t find the “right” answer, the “normal” or “socially acceptable” one.

Imagine having to talk to an NPC (non-player character) in a video game to get to the next level, knowing that all available answers will lead to a “game over”. It doesn’t make you want to play.

Further information

Inertia is a form of executive dysfunction. Executive functions are complex brain processes that enable us to take the right action in the right context, and to adjust to the environment. When a person falls into inertia, it's because they are no longer able to carry out the actions required by the situation.


People in a state of inertia don't do it on purpose. They can't simply stop their state of inertia, and it's harmful to put pressure on them to do so.

The autistic person in this state experiences great stress if they know there are negative consequences. But even if they are stressed, the person in the state of inertia continues to perceive their body with just as much sensitivity as usual, if not more. In a calm environment, with people you trust, this state can be experienced without stress. It can even be fun to think about it afterwards!

Inertia without stress

An autistic person may enter a state of inertia because they can’t find a good answer to an everyday problem. For example, how do you get into the house without getting water all over you and your socks wet when you’re covered in snow? If you take off your boots right away, your socks will get wet, it will be unpleasant and there will be traces of wet socks everywhere. But we can’t keep the boots on! There’s going to be water everywhere.

In this example, there may be a delay in choosing an action (between saving one’s socks or the floor). And very often, the snow will have time to melt, wetting feet and floor before the person can make a choice.

A similar phenomenon can occur in people with ADHD, since it’s called executive dysfunction (see definition above). In fact, inertia is like a version of executive dysfunction where you become a statue! And in the case of inertia, it always occurs at a time of emotional and/or sensory overload.

Inertia or freeze?

Autistic people may also have stress or trauma responses. All humans, and even many other animals, share the same stress responses. In the face of danger, we may fight, flee or freeze. From the outside, people in a state of inertia appear frozen. In fact, many people will describe it in the same way: “I’m frozen”. However, people who freeze in the face of danger may disconnect from their bodies to protect themselves. Anyone who experiences a traumatic event, or has experienced one in the past, can freeze and disconnect from their body.

People in a state of inertia are not dissociated. They feel their bodies, and everything is clear. They simply can’t find “the right answer” to continue their activities. The person in a state of inertia perceives their environment as usual. The frozen person experiencing a trauma will feel that reality is becoming blurred, will not perceive their body as before, and may even feel as if they are outside their body.

Un jour, j’étais dans un local et à côté de moi il y avait une grande quantité de tables, pliées, en appui sur le mur. Tout doucement, elles se sont mises à glisser. Vraiment lentement. Tout ce que j’avais à faire était de placer ma main devant et j’aurais pu les retenir. Mais en regardant les tables glisser, je n’arrivais pas à déterminer la suite des mouvements, lesquels seraient les meilleurs à poser après avoir placé ma main. Donc, devant le doute, je n’ai rien fait et tout a fini par s’écrouler. Les gens autour n’ont pas compris mon manque de réaction.

Since autistic people don’t perceive social information in the same way as allistic (non-autistic) people, it’s possible for an autistic person to freeze in front of a social situation that doesn’t seem traumatic for others.

What if the person disconnects from their body?

If you feel disconnected from your body, it’s no longer inertia. If this happens, it’s important to seek help from a psychologist. What’s more, autistic people, like all other people, can experience situations of abuse. However, it can be more difficult for autistic people to identify them. This puts them at greater risk of experiencing abuse multiple times.


Freezing is a signal that the body sends to say it has detected danger.

As soon as the body starts moving again, it’s important to seek help from a psychologist, social worker or psychotherapist. These professionals can help you understand what’s going on and find solutions to keep you safe.

Catherine Bouchard-Tremblay

Science popularizer