As families prepare for the start of a new school year, parents should be alert for signs of emotional distress in young children.

Unlikely as it may sound, children ages 6 and younger may face a host of mental-health issues, from disruptive behavior problems and attention deficit (hyperactivity) disorder to psychosis and major depression.

"It's not a discovery to us, but I know it is for the public and even for many pediatricians," says Dr. Peter Gorski, a University of South Florida pediatrician who specializes in developmental and behavioral medicine and research at the Children's Board of Hillsborough County.

Gorski says as many as 10 percent of American children will have an episode of clinically significant depression at one time or another. Starting or returning to school can be stressful and trigger emotions and anxiety in children that even the most attentive parents may miss.

"School can put (children) over the top. It has nothing to do with school, actually. That's just the place the child brings his emotional baggage," says Gorski.

Colette Parker of Tampa thought her youngest son, Xavier Williams, would handle kindergarten without much fuss, just as his older brothers did.

But two weeks into his first school year she started getting calls from his teacher. Five-year-old Xavier was throwing things, blowing up emotionally, running out of the classroom, acting aggressively and physically fighting with other children. The teacher couldn't handle him.

Parker, 33, says her son had a difficult time making the adjustment from the familiar friends and caregivers at day care to the more structured environment of kindergarten. Day care was all about play. "In school he had to sit down and do work," says Parker.

Different people, a different environment, a different routine and different expectations can all affect how a child feels and behaves in school.

"We see a lot of families who never had issues with their kids until school started," says John Mayo, a licensed child therapist and deputy executive director of Success 4 Kids & Families, a nonprofit organization that provides family-focused mental health services in Hillsborough County.

What may seem new and exciting to some kids presents an enormous emotional loss to others, he says. A change in caregivers, moving to a new home or community, divorce and a death in the family are among the most common triggers for emotional problems in young children. "Even changing from one caregiver to two or three who divide their attention between many more children, as we see in school, can be a factor," says Mayo.

Of course, events that anyone would identify as traumatic, such as violence and abuse, can also have a significant psychological impact on children.

There may also be a biochemical reason for emotional problems in children.

Beth Piecora knew something was wrong with her daughter, Kaitlyn, not long after she was born. She would cry for hours and could not be comforted. As she got older she had extreme temper tantrums, night terrors and was afraid of everyone except for a few immediate family members. She couldn't connect or interact with family friends, neighbors, aunts and uncles.

"She was so young, just 3 years old, and we didn't know what was wrong. I thought it might be some mental-health issues so we went to a psychiatrist," says Piecora, who lives in Tampa.

With family therapy, Kaitlyn improved but still had emotional problems. Piecora asked the doctor to order some medical tests. A simple blood test revealed that Kaitlyn had an underactive thyroid. "It had probably not been functioning since birth, and since thyroid regulates mood, it all started to make sense," says Piecora.

At 7 or 8 years old, her daughter was put on the thyroid hormone replacement, Synthroid. Within six months she was much more like a normal little girl. Today, Kaitlyn is 16, successful academically and very involved in church and school activities.

Piecora, who now helps lead family mental-health workshops for Success 4 Kids & Families, says it's critical for parents to realize there's a problem and reach out for help.

Parker agrees. She ignored Xavier's aggressive behavior at home for years, thinking it was normal roughhousing with his brothers and father. "I just brushed it off," she says. "I wish I had addressed it back then."

Last summer, she enrolled Xavier in Success 4 Kids & Families, which sent a behavior specialist to their home every week for six months and worked with Parker on her parenting skills. "Before the program, my house was chaotic. It helped me with dealing with all three of my boys. It made a big difference," she says.

So has medication: Xavier takes Concerta for ADHD and Clonidine to help him sleep, plus Abilify to help control his aggressive behavior.

"They have helped him a lot to be able to calm down, focus and sit through church or go with me shopping," his mother says. "Before, he was bouncing all around."

So how does a parent know the difference between a phase and a problem?

Mayo, who has worked with children for more than 27 years, says it's a matter of degree. All children can seem blue at times, or might misbehave or refuse to do homework or chores. But when these behaviors become chronic, that's another issue.

"What's the intensity of the behavior? What's the frequency of the behavior? Any kid can have a bad day, but if it's on a regular basis, that's a tip-off," he says.

When to seek help

Decline in school performance

Poor grades despite strong efforts

Constant worry or anxiety

Repeated refusal to go to school or to take part in normal activities

Hyperactivity or fidgeting

Persistent nightmares

Continuous or frequent aggression or "acting out"

Continuous or frequent rebellion and/or temper tantrums

Depression, sadness or irritability

Source: Mental Health America