Sure, teens are moody. But serious mental health issues in children and teens are more common than you might think.

About one in five teens lives with a mental health condition, according to the National Alliance on Mental Illness (NAMI). Half of them show symptoms by age 14.

Autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) are two of the most commonly diagnosed mental health issues in young people. According to NAMI, 9 percent of people under 17 have ADHD, and 1 in 68 children are on the autism spectrum (that number is rising). About 8 percent of children and teenagers will experience an anxiety disorder.

Related: ADHD May Mask Autism in Young Kids

Children and teens who have ADHD, anxiety or a family history of mood disorders are at increased risk for depression. Children who are depressed may complain of aches and pains, according to NAMI. Teens who are depressed may become aggressive, engage in risky behavior or do poorly in school. Depression puts teens at an increased risk for suicide, which is the third leading cause of death for teens ages 15 to 19, according to NAMI.

If you think your teen may be having mental health issues, start by having a conversation with his or her pediatrician.

Related: Does Your Teen Need a Therapist?

NAMI mental health for children & teens infographic(Photo: /National Alliance on Mental Illness)