Editor's note: In the comments section below, read the results of a live chat about mental illness between readers and CNN Digital Correspondent Kelly Wallace, mental health expert Dr. Charles Raison, CNN's Kat Kinsman, who has written about her personal battle with depression and anxiety, celebrity publicist and mental health advocate Terrie M. Williams and clinical social worker Devra Gordon Renner.
(CNN) -- When we lose a beloved superstar like Robin Williams to an apparent suicide and learn he had been battling severe depression before his death, it's natural to think about our own loved ones.
We might look around at our adult family members and friends who are suffering and try to get them the help they need, but what we might not see is children and adolescents can get depressed and anxious, too.
And it's more common than we probably realize.
On any given day, according to studies, it is estimated that about 2% of elementary-school-age children and about 8% of adolescents suffer from a major depression, and 1 in 5 teens has had a history of depression at some time, according to the National Alliance on Mental Illness.
But how does a parent differentiate between what might be considered normal irritability and moodiness, especially during those teenage years, and signs that something more serious is afoot?
"I think you should start worrying ... anytime there's enough of a change when you go, 'Oh my God they don't seem like themselves,'" said Dr. Charles Raison, a professor of psychiatry at the University of Arizona College of Medicine.
Raison says the timeline is key; parents should perk up if for two to three weeks their children are "unremittingly down," feeling hopeless and negative, if they start to withdraw from friends and activities, and if they experience dramatic changes in sleep.
Depressed teens might have difficulty falling asleep, not be able to fall back asleep after they wake up in the middle of the night or wake up very early in the morning. At the other end of the spectrum, they could be getting excessive amounts of sleep, sometimes sleeping 12 hours or more, psychiatrists say.
For younger kids, detecting depression gets "more complicated" for parents, Raison said, because children below the age of puberty don't necessarily show the same signs of depression as teens and adults.
"The younger the kid, the more scrambled the symptoms can be," he said. "They're easily upset. They cry more. They're scared to sleep alone at night. They become irritable. They act out more."
In younger children, parents aren't likely to see the "classic depressive pattern," Raison said. "But you're still looking for that same larger idea, which is if your kid shows a real maladaptive change in their emotions (and) their behavior, the light needs to go off in your head because something isn't right."
Melissa Atkins Wardy, a mom of two in Janesville, Wisconsin, and author of "Redefining Girly," said she was never aware that children as young as her daughter Amelia, who is now 8, could develop anxiety outside of a traumatic experience.
But halfway through first grade, Amelia said she didn't want to go to school, and reluctance to go to school "morphed into tears and nausea every day and then tears and worry at bedtime, too," said Atkins Wardy, founder and CEO of the company, Pigtail Pals & Ballcap Buddies, which creates empowering T-shirts for girls and boys.
"Eventually things just spiraled downward in second grade where her light just went out," she said. "I was like her happy childhood had been swallowed up in a dark hole."
Her daughter was eventually diagnosed as suffering from general anxiety and has been seeing a "wonderful" therapist, Atkins Wardy said, for about a year.
When help is needed
Atkins Wardy knew something was wrong and eventually sought professional help, but often parents seek reassurance by telling themselves their child will grow out of the behavior or get better, said Dr. Robert Hendren, director of child and adolescent psychiatry at the University of California, San Francisco.
When the behavior is going on for weeks, it's really time to assess what's happening, Hendren said.
The first step in the case of tweens and teens is being direct and discussing the issue head on, asking them, for instance, how they are feeling and if anything happened to make them feel unusually sad, he said.
"Most adolescents will answer," said Hendren, who is also a past president of the American Academy of Child and Adolescent Psychiatry. "One of the things that we learn a lot as health care providers is the majority of the kids that we miss who have depression and who may go on and be at risk of suicide are kids who were just never asked."
Parents can also get more information by talking to the people around their child -- teachers, coaches, youth directors, even parents of friends.
"The parent is trying to gather data: 'Is my kid just acting unhappy, uncharacteristically unhappy like this at home, or is it being noticed elsewhere outside?' because ... if it's also outside, then we're talking about a larger issue," said psychologist Carl Pickhardt, author of the book "Surviving Your Child's Adolescence" and host of a weekly blog for Psychology Today.
Of course, not many children, if any, will be excited to run off to a therapist's office if their parents determine they need outside help.
Pickhardt says he deals with this all the time. He tells parents to tell their kids that they don't have to go and see anybody by themselves, but they do need to go see someone with their parent.
"You can choose to say something or not, but at least you can be here to hear what my concerns are and hear what the other person has to say," said Pickhardt, relaying the script he gives parents to use with their children.
"I've never had a kid not participate," he added.
Signs of suicide risk
Another huge challenge for parents is trying to determine when their child is at risk of suicide.
Hendren, who is also a professor of psychiatry at the University of California, San Francisco, recommends parents ask their children who appear depressed if they ever feel like their life is not worth living, or if they have ever thought about taking their own life.
Raising the issue does not give children the idea of suicide, said Hendren, putting to rest concerns that many parents might have.
"All the studies seem to indicate that you don't have somebody start thinking about suicide by asking them about it. They're either thinking about it or they're not."
That doesn't mean it's an easy discussion for any parent, said Devra Gordon Renner, a clinical social worker in Northern Virginia who has helped hundreds of families deal with childhood depression and anxiety.
"Saying to somebody, 'Are you thinking of harming yourself?' -- that's not a comfortable conversation for a parent to have with a child. But it is a healthy conversation, because it is acknowledging that your child may be feeling really bad and letting them know you are there to help and you are taking them seriously," said Gordon Renner, who is also the co-author of "Mommy Guilt."
When a child says he or she has thoughts that life is not worth living and has considered suicide, those are "ominous signs" that would call for an evaluation by a medical professional experienced with depression and suicide, Hendren said.
"If ... alcohol or other substances might be involved, then the risks really jump because in an altered state of mind, kids seem at a higher risk of doing something that might be harmful."
The stigma remains
Because of the stigma of depression and suicide, too many people are still hesitant to talk about it, even when talking about it helps people who are suffering realize they are not alone, experts say.
"'It's amazing that once you start talking about this, other people pop up with, 'Oh, my cousin had this, my sister had that,'" said Gordon Renner.
"Depression is an illness and it's a treatable illness, and in some cases it can metastasize and be fatal for some people, and I think it's important to know that, but it's rare," she added.
It was the stigma, in part, that drove Atkins Wardy to publicly share her daughter's battle with anxiety on Facebook. At first she questioned whether she was compromising her daughter's privacy.
But since her daughter's battle was already public as far as her school community was concerned, and after getting private messages from mothers looking for advice to help their daughters who also struggled with anxiety, Atkins Wardy decided the issue was bigger than her and her daughter.
"Ultimately, the reason I have continued to share our journey with childhood anxiety is that it is so greatly misunderstood and parents need help," she said.
"Had people who had experienced childhood anxiety not been brave enough to reach out to me and teach me what Amelia was experiencing, I think I would have made some really bad parenting choices."
As for her daughter, who went on a low dose of medication a short time ago, she is pretty much back to her old self again.
"We have our girl back. This is the person I knew was hiding under the mask of anxiety and I was willing to do anything to get her out."
For any information on how to talk to a child about depression or where to find help, contact the National Association of Mental Illness.