Krystal M. Lewis, PhD is a licensed Clinical Psychologist and Co-Director of Education with the Section on Development and Affective Neuroscience at the National Institute of Mental Health (NIMH) and the Director of the Clinical Psychology Externship Program at the National Institutes of Health. Her group at NIMH (SDAN) studies how information processing in the brain may vary across youth with symptoms of anxiety and depression using neuroimaging and biobehavioral methodology. Dr. Lewis completed her pre-doctoral internship and post-doctoral fellowship training at Ann & Robert H. Lurie Children’s Hospital in Chicago. Dr. Lewis is passionate about the provision of clinical care, training, and mentorship and uses culturally informed, developmentally appropriate, and evidence-based treatment approaches. Her clinical and research interests are focused on identifying mechanisms of change in psychological treatment for pediatric anxiety and mood disorders.
Article3 min read
What Is Generalized Anxiety Disorder (GAD) and What Causes It?
- Krystal M Lewis PhD
- Oct 1, 2025
- 3
If unrelenting stress and worry are making it nearly impossible to get through the day, you may be suffering from more than everyday anxiety. Generalized anxiety disorder, or GAD, affects an estimated 300 million people globally—4% of the world’s population—each year. This group primarily consists of women, who are twice as likely to be diagnosed with anxiety as men.
What Is Generalized Anxiety Disorder (GAD)?
Generalized anxiety disorder, or GAD, is a mental health condition primarily characterized by persistent and excessive worry. Someone suffering from GAD may feel stressed about any number of specific issues –money, work, health, or relationships, for example –or everything in general and nothing in particular. Their responses to stressors will typically seem more severe than the reactions of others in similar circumstances.
Generalized Anxiety Disorder Symptoms
To diagnose you with generalized anxiety disorder, a healthcare provider will conduct a screening to see if you’ve had at least three anxiety symptoms for an ongoing period of six months or longer. Common GAD symptoms include:
- Irritability
- Brain fog or difficulty focusing
- Getting tired easily
- A general feeling of restlessness or being on edge
- Muscle tension
- Disturbed sleep
- Headaches
- Gastrointestinal discomfort
Do I Have Normal Anxiety or Generalized Anxiety Disorder?
Anxiety is a natural and even healthy part of life; it’s your body’s way of keeping you safe by alerting you to potential hazards. Feeling worried every now and then, particularly in the midst of stressful circumstances, is completely normal and not indicative of GAD.
Certain symptoms and patterns, however, can indicate that you should meet with a qualified healthcare provider to discuss the possibility of generalized anxiety disorder. These include:
- Stress responses that feel more intense than the situation calls for
- Symptoms that seem overwhelming or out of your control
- Panic that persists despite reassurance that everything is okay
- Anxiety that interferes with your ability to participate in or enjoy daily activities
Quiz: Am I Experiencing Normal Anxiety or Generalized Anxiety Disorder?
| Normal anxiety | Generalized anxiety disorder |
| I feel tired and sore after sitting through a stressful day at work or pushing myself too hard at the gym. | I’ve been experiencing fatigue, restlessness, and muscle tension for more than six months and can’t seem to pinpoint a cause. |
| I’m worried about an upcoming work deadline, university exam, or doctor’s appointment. | Chronic worry disrupts my everyday life. It interferes with my work, school, family, and social lives. |
| I’m having trouble sleeping or concentrating after losing my job, going through a breakup, or experiencing another hardship. | I regularly feel irritable, can’t focus, and struggle to sleep; it feels like I have more bad days than good. This has been ongoing for at least six months. |
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