Maybe you’ve had panic attacks before. Yet, they always seem to feel slightly different from the last time or come at unexpected times. Are there different types?

Panic attacks can feel different in how intense they are and how long they last — from one attack to the next and from one to person to another.

What causes you to experience a panic attack can also vary, and sometimes, take you completely by surprise.

While most people will have a panic attack at some point, it doesn’t mean they’ll have others. But if you do have repeated panic attacks, it can sometimes be a sign of an anxiety disorder.

A panic attack is a very sudden and intense episode of anxiety brought on by a perceived or real threat. It causes an extreme response in your body.

Panic attacks happen for any number of reasons, and they’re not necessarily a symptom of a mental health condition.

Anyone can have a panic attack. However, some people who have panic attacks and persistent anxiety about having these attacks can develop panic disorder. Not everyone who has panic attacks will have panic disorder, though.

During a panic attack, you can experience symptoms that are mental, physical, emotional, and cognitive — all at once.

According to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) if four or more of the symptoms below are experienced during an anxiety episode, the event will be considered a panic attack:

  • heart palpitations
  • sweating
  • trembling or shaking
  • shortness of breath
  • feeling as if you’re choking or being smothered
  • chest pain
  • nausea or abdominal discomfort
  • dizziness or lightheadedness
  • derealization or depersonalization
  • fear of losing control or dying
  • numbness or tingling
  • chills or hot flashes

The abruptness and intensity of a panic attack can often be the most unsettling part, leading some people to believe they’re having a heart attack or are in danger. This can leave you feeling exhausted and shaky afterward.

There are two characteristic types of panic attacks: unexpected and expected. They’re classified this way depending on the trigger and onset. The symptoms, however, can be the same for both types.

Unexpected panic attacks have no evident cause or trigger. This means that you’ll have a difficult time pinpointing what caused your attack.

For example, you may be listening to music on the floor and suddenly experience a panic attack. Because you were relaxed and resting, you’d say this was an unexpected panic attack.

An unexpected panic attack can happen while you’re asleep, when you’re with friends, or while eating at your favorite restaurant.

This doesn’t mean there’s actually no trigger — it’s just very hard to identify it.

The exact cause of unexpected panic attacks isn’t well understood. It may be your brain picking up on cues in the environment before your conscious self does. It may be unconscious associations to times when you’ve felt fear.

For instance, a song, lighting effect, or perfume might lead your brain to associate the current moment with another time when you felt pain or fear. This could prompt a panic attack without you realizing what the trigger was.

In other cases, anxiety itself triggers the panic attack.

Say that you’ve been very stressed lately and feel anxious about losing your job. Today you decide to do some gardening to relax. Instead, you suddenly feel your heart racing and a bit lightheaded. You immediately worry about these symptoms and that brings on new sensations. You experience an unexpected panic attack.

In any case, what triggers a panic attack for you may be completely different from someone else’s triggers. And most people find they have multiple triggers.

Unexpected panic attacks can catch you off guard, leading to even greater feelings of fear and stress.

Panic disorder is usually diagnosed if you have repeated unexpected panic attacks.

Expected panic attacks are usually linked to known stressors and specific triggers.

For example, you may fear crowds, flying, or spiders. You could experience a panic attack if exposed to any of these. In that case, you’d know your panic attack was linked to that object or event.

Expected panic attacks can be situationally cued or predisposed.

A situationally cued panic attack can happen immediately after you’re exposed to a similar situation that has given you anxiety before or where you previously experienced a traumatic event.

For example, being back in a particular park where a dog bit you could trigger a cued panic attack as soon as you step on the lawn.

Predisposed panic attacks are slightly different in that they may not happen immediately after being exposed to the trigger.

Your fear or phobia is consistent, but you might experience your panic attack before, during, or after the event or exposure.

So let’s say oral exams or presentations give you high levels of anxiety. You have an important oral exam coming up at school and you’re feeling very anxious about it. You may have a panic attack the night before, during, or long after you’ve finished your exam. The trigger is clear, but the onset of the episode can vary.

Expected panic attacks are more common for people with generalized anxiety disorder, agoraphobia, or social anxiety.

Panic attacks involve intense and sudden anxiety symptoms that usually peak in a few minutes. The two types of panic attacks are expected and unexpected.

Expected panic attacks can usually be predicted, since you’ll know what triggers them. Unexpected panic attacks come “out of the blue” without an apparent cause.

Anyone can have a panic attack. Panic attacks can be a symptom of an anxiety disorder, such as panic disorder, along with other mental health and physical conditions.