Panic attacks typically begin suddenly, without warning. They can strike at any time — when you're driving a car, at the mall, sound asleep or in the middle of a business meeting. You may have occasional panic attacks, or they may occur frequently.

Panic attacks have many variations, but symptoms usually peak within minutes. You may feel fatigued and worn out after a panic attack subsides.

Panic attacks typically include some of these signs or symptoms:

• Sense of impending doom or danger
• Fear of loss of control or death
• Rapid, pounding heart rate
• Sweating
• Trembling or shaking
• Shortness of breath or tightness in your throat
• Chills
• Hot flashes
• Nausea
• Abdominal cramping
• Chest pain
• Headache
• Dizziness, lightheadedness or faintness
• Numbness or tingling sensation
• Feeling of unreality or detachment

One of the worst things about panic attacks is the intense fear that you'll have another one. You may fear having panic attacks so much that you avoid certain situations where they may occur.

It's not known what causes panic attacks or panic disorder, but these factors may play a role:

• Genetics
• Major stress
• Temperament that is more sensitive to stress or prone to negative emotions
• Certain changes in the way parts of your brain function

Panic attacks may come on suddenly and without warning at first, but over time, they're usually triggered by certain situations.

Some research suggests that your body's natural fight-or-flight response to danger is involved in panic attacks. For example, if a grizzly bear came after you, your body would react instinctively. Your heart rate and breathing would speed up as your body prepared for a life-threatening situation. Many of the same reactions occur in a panic attack. But it's unknown why a panic attack occurs when there's no obvious danger present.

Symptoms of panic disorder often start in the late teens or early adulthood and affect more women than men.

Factors that may increase the risk of developing panic attacks or panic disorder include:

• Family history of panic attacks or panic disorder
• Major life stress, such as the death or serious illness of a loved one
• A traumatic event, such as sexual assault or a serious accident
• Major changes in your life, such as a divorce or the addition of a baby
• Smoking or excessive caffeine intake
• History of childhood physical or sexual abuse

Left untreated, panic attacks and panic disorder can affect almost every area of your life. You may be so afraid of having more panic attacks that you live in a constant state of fear, ruining your quality of life.

Complications that panic attacks may cause or be linked to include:

• Development of specific phobias, such as fear of driving or leaving your home
• Frequent medical care for health concerns and other medical conditions
• Avoidance of social situations
• Problems at work or school
• Depression, anxiety disorders and other psychiatric disorders
• Increased risk of suicide or suicidal thoughts
• Alcohol or other substance misuse
• Financial problems

For some people, panic disorder may include agoraphobia — avoiding places or situations that cause you anxiety because you fear being unable to escape or get help if you have a panic attack. Or you may become reliant on others to be with you in order to leave your home.