American Academy of Child & Adolescent Psychiatry: All children experience anxiety. Anxiety in children is expected and normal at specific times in development. For example, from approximately age 8 months through the preschool years, healthy youngsters may show intense distress (anxiety) at times of separation from their parents or other caregivers with whom they are close. Young children may have short-lived fears, (such as fear of the dark, storms, animals, or strangers).
Anxious children are often overly tense or uptight. Some may seek a lot of reassurance, and their worries may interfere with activities. Parents should not discount a child's fears. Because anxious children may also be quiet, compliant and eager to please, their difficulties may be missed. Parents should be alert to the signs of severe anxiety so they can intervene early to prevent complications.
New situations, challenging tasks, and even unfamiliar people can lead to fear and anxiety in children from time to time.
Other age-appropriate fears include:
Stranger anxiety beginning at 7 to 9 months of age
Fear of the dark, monsters, insects, and animals in preschoolers
Fear of heights or storms in younger school-age children
Worry about school and friends in older school-age children and teens
It takes a little more than occasional anxiety, which can be normal, to indicate true symptoms of an anxiety disorder.
Childhood Anxiety Symptoms
As much as it is common to have occasional anxiety, it is also common for children to have anxiety disorders. 
Children with true anxiety symptoms have them on most days and they can include:
Trouble sleeping (insomnia)
Anxiety and depression can be caused by various traumatic experiences.
1. Freidl EK, Stroeh OM, Elkins RM, Steinberg E, Albano AM, Rynn M. Assessment and treatment of anxiety among children and adolescents. Focus (Am Psychiatr Publ). 2017;15(2):144-156. doi:10.1176/appi.focus.20160047
2. Gale CK, Millichamp J. Generalised anxiety disorder in children and adolescents. BMJ Clin Evid. 2016;2016
These scientifically supported sites are among psychology’s best for helping parents raise their kids.
Choose each topic of interest to view resource:
HealthyChildren.org - from the American Academy of Pediatrics. Anxiety in Teens is Rising: What's Going On? Whatever the cause, this rise in anxiety is a real problem for our youth.
Effective Child Therapy - Evidence based mental health treatment for children & adolescents.
What is Anxiety? When is Anxiety a Problem for a Child? Effective Therapies Tested Therapies for Young Children Under 8.
Anxiety, Worries and Fear: a Normal Part of Childhood Finding Professional Help/Treatment for Children How to Support Your Child with Anxiety Financial Support for Children with Anxiety Types of Anxiety in Children Causes of Anxiety in Children
All children experience some anxiety. Anxiety in children is expected and normal at specific times in development. For example, from approximately age 8 months through the preschool years, healthy youngsters may show intense distress (anxiety) at times of separation from their parents or other people with whom they are close. Young children may have short-lived fears, such as fear of the dark, storms, animals, or a fear of strangers. Included information:
Symptoms of Separation Anxiety, Symptoms of Phobia, Symptoms of Social Anxiety,
Other symptoms of anxious children
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.