A new study published in the Journal of Developmental & Behavioral Pediatrics shows that around 2.6 million children and teens had diagnosed depression and/or anxiety in 2011-12.
As well, the researchers found that the number of children with diagnosed anxiety has risen in recent years, but not depression.
The team looked at data from the National Survey of Children's Health for 2003, 2007, and 2011-12. Parents were asked about their children aged six to 17 and whether or not their kids had diagnosed depression or anxiety.
The report found that the number of kids suffering from current anxiety rose from 3.5 percent in 2007 to 4.1 percent in 2011/12.
The number of children in the US with current depression showed no significant change, with 2.5 percent in 2007 and 2.7 percent in 2011/12.
5.3 percent of children and adolescents had anxiety and/or depression at the time of the survey in 2011/12.
The study's lead author, Rebecca H. Bitsko, PhD, of the National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, and her co-authors wrote:
"These estimates correspond with approximately two million children aged six to 17 years in 2011-12 with current anxiety, 1.4 million children with current depression, 2.6 million with current anxiety or depression, and 760,000 children with both."
The percentage of kids who had ever been diagnosed with anxiety or depression rose from 5.4 percent in 2003 to 8.4 percent in 2011/12.
The report found that children with either of these mental health issues were also more likely to suffer from a chronic health condition, including obesity or neurobehavioural disorders.
Having anxiety or depression was linked to more issues at school, increased use of healthcare services, and higher levels of aggravation for parents, even after adjusting for other health problems.
"Despite significant healthcare needs, nearly 20 percent of children with anxiety or depression did not receive mental health treatment in the past year," the authors noted.
As well, only about a third of these kids had a 'medical home', another term for a usual source of healthcare services.
It is unclear whether the uptick in child anxiety that the study found is due to increased awareness around the signs of anxiety, or an increase in kids experiencing anxiety symptoms.
As well, this national report has higher estimates than community-based studies, 'suggesting that child anxiety may be under-diagnosed'.
"Children with anxiety and depression may have needs that go beyond diagnosis and mental health treatment," Dr Bitsko told Science Daily.
"Anxiety and depression are associated with school problems, parenting stress, and unmet medical needs. Parents, healthcare providers, and teachers can look for ways to support children with anxiety and depression in all areas of the child's life."
If you are worried your child suffers from anxiety, depression, or any other mental health issues, visit https://youngminds.org.uk/ or talk to your GP.