An Acute Anxiety Disorder, or Acute Anxiety State as it is sometimes known, is when the person is overcome by anxious feelings almost constantly usually as a result of something that has happened in their life. Many instances of what is known as a 'nervous breakdown' would probably be diagnosed as this.
What happens here is that the arousal system becomes sort of stuck in the high position.
For a diagnosis of Post Traumatic Stress Disorder the person has to have experienced some kind of specific traumatic event during which they had reason to believe they might die. This then causes the survival instinct to become overactive and look for danger in all sorts of places it doesn't usually.
Acute Anxiety Disorder there is also ongoing raised negative arousal but this has built up as a result of several smaller unsettling situations which happened too close together for the person to be able to resolve them and enable their arousal system to return to its normal level between each one.
The result is that with each stressful situation, the arousal system is already starting from a higher level In the end it gets so high that it gets stuck up there.
At that point the sufferer inadvertently adds to the problem by worrying about the way they feel and the fact that they can no longer control their lives, and so it goes on... They are becoming stuck in a spiral of anxiety/raised negative arousal itself causing more of the same and the acute anxiety disorder/state develops.
Let's consider, for example, someone who is being bullied at work.
In this example suppose this person is unable to stand up to the bullying. The first time it happens they may experience some negative arousal but may try and put it out of their mind, hoping it was a one off.
But the survival instinct will have logged this event in its records. When it happens a second time, the arousal level will go a bit higher, and the survival instinct will increase the possible danger score.
Each time it happens the person will be more affected by it. The survival instinct will have associated it with the workplace and may have started putting warnings into the person's head as they leave the house for work. This thought alone will trigger further negative arousal. Before long the person is feeling this same negative arousal when they go to bed at night because they know they have to go to work the next day. They may even start to have nightmares about work and being out of control there etc.
At this point some people will go to their doctor and go sick for a while.
This of course does nothing to change the situation at work and they then find that they are reluctant to come off the sick and go back. This makes them feel guilty, they start thinking that others believe they are wasters because there doesn't appear to be anything wrong with them but they can't explain what's wrong and they feel they should be at work. If acquaintances ask what's wrong the sufferer is often afraid others will think they're going mad if they say they have an acute anxiety disorder. Having any type of psychological disorder is still considered un-macho for men in many communities.
If such a person is also prone to anxiety or even to panic attacks, these will most probably be getting worse as the negative arousal level remains high. Then all it takes is for some other normally fairly minor event to happen, maybe a bump in the car, worries about money, etc to push that person into constant negative high arousal. They then feel totally out of control and so the negative raised arousal goes on.
In our example, even if the person managed to return to work, if nothing had been done to either help them to deal with the bullying or to stop it, it wouldn't be long before the negative raised arousal kept repeating and the person ended up unable to go to work again.
In my own case, the trigger for my panic attacks had always been blood or accident related. When I had my Acute Anxiety Disorder for two months some thirty years ago, I recall my neighbour coming round for coffee one morning. As I opened the door to her I said, "Before you come in, if you've had so much as a splinter in your finger, please don't tell me about it!" At that point even a tiny splinter would have be sufficient to cause a panic attack.
There are more details about Panic Disorder in its own section.