What are the warning signs of mental illness in children? Warning signs that your child might have a mental health condition include:

Mood changes. Look for feelings of sadness or withdrawal that last at least two weeks or severe mood swings that cause problems in relationships at home or school.
Intense feelings. Be aware of feelings of overwhelming fear for no reason — sometimes with a racing heart or fast breathing — or worries or fears intense enough to interfere with daily activities.
Behavior changes. These include drastic changes in behavior or personality, as well as dangerous or out-of-control behavior. Fighting frequently, using weapons and expressing a desire to badly hurt others also are warning signs.
Difficulty concentrating. Look for signs of trouble focusing or sitting still, both of which might lead to poor performance in school.
Unexplained weight loss. A sudden loss of appetite, frequent vomiting or use of laxatives might indicate an eating disorder.
Physical symptoms. Compared with adults, children with a mental health condition might develop headaches and stomachaches rather than sadness or anxiety.
Physical harm. Sometimes a mental health condition leads to self-injury, also called self-harm. This is the act of deliberately harming your own body, such as cutting or burning yourself. Children with a mental health condition also might develop suicidal thoughts or attempt suicide.
Substance abuse. Some kids use drugs or alcohol to try to cope with their feelings.