Anxiety is hard to describe from the inside. For one person it is a mind that will not stop running through what could go wrong. For another it is a knot in the stomach before every meeting, or a week of bad sleep with no obvious cause. Often it is several of these at once.
This article describes how anxiety tends to show up in thoughts, feelings, the body and behavior, using the descriptions given by the National Institute of Mental Health (NIMH), MedlinePlus and the American Psychiatric Association. It is a description, not a test. Only a clinician who has talked with you can say whether what you feel is an anxiety disorder.
What is anxiety, in plain words?
MedlinePlus, the National Library of Medicine's health site, describes anxiety as "a feeling of fear, dread, and uneasiness." The American Psychological Association's dictionary describes an emotion made up of apprehension and bodily tension, in a person who anticipates danger or misfortune ahead.
The same dictionary separates anxiety from fear. Fear is a short-lived response to a specific threat that is clearly identifiable and present. Anxiety looks ahead. It lasts longer and is focused on a diffuse threat, something that might happen and is hard to pin down. With anxiety there is often nothing concrete to run from or to resolve.
NIMH puts the starting point plainly: "Feeling anxious is a normal part of life." How anxiety differs from stress and everyday worry is covered in anxiety, stress or ordinary worry.
What does anxiety do to your thoughts and feelings?
It fills them with worry. The American Psychiatric Association groups the emotional symptoms of anxiety as persistent worry or fear, feeling on edge and difficulty concentrating. MedlinePlus describes anxious thoughts that are hard to control.
NIMH's description of generalized anxiety, the form built around worry, fills in the picture. People may worry excessively about everyday things, have trouble controlling the worry, feel irritable, restless or on edge, and have a hard time concentrating.
In daily life this can look like rehearsing a conversation for hours, rereading an email five times before sending it, or being unable to enjoy a free evening because your mind keeps scanning for what you forgot. Some people who feel this way look calm and capable from the outside. The practice writes about that pattern, including perfectionism and a harsh inner critic, in how therapy helps high-functioning anxiety.
Why does anxiety feel so physical?
Because the body is part of it. MedlinePlus explains that when you are stressed, your body releases certain hormones that can raise your blood pressure, heart rate and blood sugar. This reaction is sometimes called the "fight or flight" response. The sources used here do not tie each symptom of anxiety to that response. The physical symptoms they list for anxiety are these:
- Heart and breathing: a pounding or rapid heartbeat and shortness of breath (MedlinePlus, American Psychiatric Association).
- Muscles: tension, aches, trembling or twitching (NIMH).
- Head and stomach: headaches, stomachaches, dizziness or feeling lightheaded (NIMH, MedlinePlus).
- Other signs: sweating a lot, a hard time swallowing and frequent trips to the bathroom (NIMH).
- Sleep and energy: trouble falling or staying asleep, and fatigue (NIMH).
These symptoms overlap with medical conditions. That is why the American Psychiatric Association says the first step is often to see your doctor, to rule out conditions that may cause similar symptoms. Chest pain or shortness of breath that is new, severe or unexplained is a reason to call 911. The American Heart Association lists both among the warning signs of a heart attack. Do not assume it is anxiety. Physical symptoms of anxiety and when to see a doctor goes into detail.
What does anxiety do to behavior?
It pushes you to avoid. The American Psychiatric Association lists three behavioral signs: avoiding feared situations, seeking reassurance, and difficulty completing daily tasks. MedlinePlus also lists avoiding everyday activities among the symptoms of anxiety disorders.
Avoidance is not always obvious. It can be turning down an invitation, putting off a phone call, taking the long way around, or asking a partner once more whether everything is all right. Each one makes sense in the moment. Added together, they can make a life smaller.
Nights are often affected too. For what the sources say about sleep, see anxiety at night. For sudden surges of fear with strong physical symptoms, see panic attacks.
How common is it to feel this way?
Common. The Centers for Disease Control and Prevention (CDC) reported results from the 2019 National Health Interview Survey, which used a seven-item screening questionnaire called the GAD-7. In the previous 2 weeks, 9.5% of adults had mild symptoms of anxiety, 3.4% had moderate symptoms and 2.7% had severe symptoms. The other 84.4% had no or minimal symptoms.
Added together, that is 15.6% of adults, about one in six, with at least mild symptoms in a 2-week period. Mild, moderate or severe symptoms were reported by 19.0% of women and 11.9% of men.
A screening questionnaire counts symptoms. It is not a diagnosis, so these figures do not show how many people have an anxiety disorder. They do show that if you feel anxious, you have a great deal of company.
When is it more than ordinary anxiety?
There is no sharp line, and a web page cannot draw one for you. The American Psychiatric Association says that for a diagnosis of an anxiety disorder, symptoms must be out of proportion to the situation, persistent, and interfere with daily functioning. NIMH describes anxiety that does not go away, is felt in many situations and can get worse over time.
NIMH's advice on when to act is practical. When anxiety starts to cause problems in everyday life, such as at school, at work, or with friends and family, "it's time to seek professional help." Do I need therapy for anxiety? looks at that question honestly, including the fact that not everyone does.
Dr. Rabin is a licensed clinical psychologist who offers anxiety therapy in Brookline and by secure telehealth across Massachusetts. Her approach is psychodynamic, attachment-based, trauma-informed and mindfulness-based. It looks at what drives the anxiety as well as how to respond to anxious thoughts and physical sensations in the moment. You can request a free consultation of about 15 minutes through the contact page.
Keep reading
Sources
- MedlinePlus (National Library of Medicine), Anxiety (last updated October 17, 2023)
- American Psychological Association, APA Dictionary of Psychology: anxiety (updated 2018)
- American Psychiatric Association, What are Anxiety Disorders? (physician review May 2026)
- National Institute of Mental Health, Anxiety Disorders (last reviewed December 2024)
- National Institute of Mental Health, Generalized Anxiety Disorder: What You Need to Know (revised 2025)
- MedlinePlus, Stress (last updated October 20, 2023)
- Terlizzi EP, Villarroel MA, Symptoms of Generalized Anxiety Disorder Among Adults: United States, 2019. NCHS Data Brief No. 378 (2020)
- American Heart Association, Warning Signs of a Heart Attack (last reviewed December 12, 2024)
Last reviewed October 2026. This guide is general information, not medical advice or a diagnosis. If you are in crisis, call or text 988, or call 911 in an emergency.
