Panic attacks are brief episodes of extreme fear. They are extremely frightening and bewildering, so much so that during an attack one cannot think, plan, or reason. The upset they produce can be so extreme that they may be mistaken for a heart attack or stroke, and the cause is typically unknown to the person experiencing them.
Panic attacks can produce more panic attacks; that is, the fear of having another attack produces the factors that cause them. A panic attack can happen without an obvious cause, which is why they are so unsettling.
Despite the extreme nature of these attacks, they are eminently treatable. Once sufferers understand the dynamics of their particular panic attacks, the anxiety that contributes to them typically subsides. They can be overcome with effective therapy.