Children go through different stages in their life that can alter how they perceive and interact with the world. Changes in behaviors and attitudes may be seen as "just a stage" or brushed off with hopes that "it'll will go away on its own." However, these all too common phrases could potentially mask serious signs of a mental illness.

Researchers from Harvard Medical School found that half of all lifetime cases of mental disorders start by age 14 and three-fourths by 24 years of age. Because of the early onset of mental disorders, treatment and appropriate services should be accessed early. In the first report on the prevalence of specific mental disorders among American children ages 3-17, the U.S. Centers for Disease Control and Prevention (CDC) found that up to one out of five children have a mental disorder.

Attention deficit hyperactivity disorder (ADHD), disruptive behavioral disorders such as oppositional defiant disorder (OOD) and conduct disorder (CO), autism spectrum disorders, mood and anxiety disorders like depression, substance use disorders, and Tourette's were among the most prevalent mental diseases found in the target age group.

Parents can reduce the severity of childhood mental health illnesses by paying attention to common warning signs in children and seeking help when appropriate. "Major mental illnesses such as schizophrenia or bipolar disorder rarely appear "out of the blue," the American Psychiatric Association (APA) writes. Parents should go with their intuition when they see "something is not quite right" in their kids.

Do you know what symptoms to look for in your child when they exhibit peculiar behaviors and attitudes? Below you will find five warning signs of common mental health disorders in childhood.

1. Long-lasting mood swings.

A change in mood that lasts for two weeks can be a strong indicator of a serious mental disorder in your child. These mood swings which usually range from being hyperactive to being melancholy within a short time span with no substantial reason can be an early sign of bipolar disorder or manic-depressive illness. According to the National Institute of Mental Health (NIMH), the "up" or mania children feel and the "down" or depression is so powerful that it can interfere with a child's academic and social life. One-third of the 3.4 million children and teens who are diagnosed with depression may be experiencing the early onset of bipolar disorder, the American Academy of Child and Adolescent Psychiatry (AACAP) reports. Abrupt mood swings and hyperactivity accompanied by lethargy have the potential to produce a chronic irritability.

If a child becomes hyperactive without being lethargic afterward, that is a normal characteristic of childhood behavior. "Childhood bipolar disorder is characterized by many of these symptoms, taken together, and marked by rapid mood swings and hyperactivity," says John M. Grohol, Psy.D. He believes these symptoms in bipolar disorder will affect the child severely, occur frequently and lasts for approximately two weeks.

2. Excessive fears or worries.

Fears and worries in children are common throughout early childhood. It is normal for toddlers to fear the dark, imaginary creatures like "the boogie man," and being separated from their legal guardians. For grade-school children, being anxious before school performance and worrying about social acceptance among peers are seen as healthy responses that continue into adulthood. However, when these normal aged-based fears become so excessive that they interfere with a child's daily functions, it is time to have an intervention.

Children who are diagnosed with anxiety often express a specific worry or fear says the AACAP. Physical complaints are often accompanied by the worry or fear communicated by the child, which helps clinicians diagnose specific anxiety disorders.

3. Extreme behavioral changes.

Childhood defiance and questioning authority are also common behaviors in kids. Often times this behavior is motivated by the thrill of testing whether they can really get away with something without their parents' blessing. However, is your child just experimenting with independence or is there a more serious issue? Oppositional defiant disorder (OOD), on average, begins when a child is 8 years old and usually starts before the early teen years, according to the Mayo Clinic. An example of an alarming behavior would be one that displays defiance for the sake of defiance, such as buying multiple video games without any genuine interest to actually play these games. Mental health illnesses that are closely related to sporadic behavioral changes include ADHD, anxiety, bipolar, and depression.

4. Physical changes, such as weight gain or loss.

An estimated 80 percent of people with serious mental illnesses are overweight or obese, reports the National Institutes of Health (NIH). A sudden change in physical appearance that does not follow from puberty may be a strong indicator that your child is suffering from a disorder. Similarly, weight loss brought on by lack of appetite may be an early sign of depression.

Body changes brought on by alcohol or drugs to "self-medicate" are symptomatic of depressed youth, signaling a lack of concern for or attention to their appearance says the Kansas State Department of Education (KSDE). Furthermore, KSDE suggests that mental health professionals believe a child has a greater chance of developing depression if one or both of their parents suffered from the illness.

5. Lack of concentration.

Children who have extreme difficulty concentrating could potentially have a mental disorder. It is important to distinguish a child who merely wants to watch his or her favorite television show instead of doing homework, versus a child who is incapable of focusing on their favorite TV show. The inability to concentrate on a simple task is a symptom of ADHD or depression reports Psych Central. Lack of focus might result from excessive thoughts of shame, guilt, death and dying, which could be highly dangerous leading to thoughts about suicide. Trouble concentrating in a child with a disorder often manifests in their academic and social life.

These five warning signs of common mental health problems will equip you as a parent to seek the help your child deserves.