When you have a headache, you know there are many possible causes, ranging from the mild to the very serious. When you see your doctor, she will likely ask you detailed questions about how long the headaches have been taking place, what type of pain you are feeling, when they occur, and what other symptoms you’re experiencing. Without a thorough assessment and examination, it would be absurd for your doctor to diagnose you with a brain tumor or the flu, both of which can give you a headache. And, of course, the treatment for a brain tumor and a virus would look very different.

The same thing is true of mental illness: many common symptoms occur for a variety of reasons and can reflect several different diagnoses. That’s why a good mental health professional will give your child a thorough evaluation based on a broad range of information before coming up with a diagnosis. It’s crucial to understand what’s really behind a given behavior because, just as in medicine, the diagnosis your child receives can drastically change the appropriate treatment. ADHD medications, for example, won’t work if a child’s inattention or disruptive behavior is caused by anxiety, not ADHD. And, just like a medical doctor, when a treatment doesn’t work, whether it’s therapeutic or pharmaceutical, one of the things a good clinician will do is reexamine the diagnosis.

Here we take a look at some of the common psychiatric symptoms that are easily misinterpreted in children and teenagers, leading to misdiagnosis. For each symptom, we explain the diagnosis it is commonly linked to, and what some of the alternate causes for what that behavior might be. (This list is only meant to be used as a guide, and it is important to always consult with a trained diagnostician before beginning treatment or assigning a label to your child.)

1. Inattention

The common diagnosis: ADHD

The symptom of inattention is often first observed by teachers, who may notice a student who is unusually easily distracted, is prone to daydreaming and has difficulty completing homework assignments and following directions. While all children, especially those who are very young, tend to have shorter attention spans than adults, some children have much more trouble focusing than others.

Inattention that is outside the typical range is one of the three key symptoms of ADHD, along with impulsivity, and hyperactivity. So when a child seems unusually distracted ADHD tends to be the first thing parents and clinicians suspect. However, there are many other possibilities that can be contributing to inattention.

“The kid who is inattentive could be inattentive because he has ADHD,” notes psychologist Steven Kurtz. “Or he could be inattentive because he is worried about his grandmother who’s sick in the hospital, or because he’s being bullied on the playground and the next period is recess.”

Related: Is It ADHD or Immaturity?

Other Possibilities:

Obsessive-Compulsive Disorder:

Many children with OCD are distracted by their obsessions and compulsions, and when the OCD is severe enough, they can spend the majority of their day obsessing. This can interfere with their lives in many ways, including paying attention in school. And since children with OCD are often ashamed of their symptoms, they may go to great lengths to hide their compulsions. It is not uncommon to see children keep their rituals under control while they are at school, only to be overwhelmed by them when they get home. Therefore, a teacher may notice a student having difficulty focusing and assume he has an attention problem since his OCD is not apparent to her.

“A kid may be sitting in the class having an obsession about needing to fix something, to avoid something terrible happening. Then the teacher calls on him,” says Dr. Jerry Bubrick, a clinical psychologist at the Child Mind Institute. “When he doesn’t know the answer to the question, it looks like he wasn’t paying attention, but it’s really because he was obsessing.”

Post-Traumatic Stress Disorder:

Children can also appear to be suffering from inattention when they have been impacted by a trauma. “Many of the symptoms of PTSD look like ADHD,” explains Dr. Jamie Howard, the director of the Trauma Response and Education Service at the Child Mind Institute. “Symptoms common in PTSD, such as difficulty concentrating, exaggerated startle response, and hypervigilance can make it seem like a child is jumpy and spacy.”

Learning Disorder:

When a child seems to be looking everywhere but at the pages of the book she is supposed to be reading, another possible cause is that she has a learning disorder. Undiagnosed dyslexia can not only make a youngster fidget with frustration, she may be ashamed that she doesn’t seem to be able to do what the other kids can do, and intent on covering that fact up. Feeling like a failure is a big impediment to concentration and anything that might relieve the feeling a welcome distraction.

“Fifty percent of kids who have learning disabilities have inattention,” notes Dr. Nancy Rappaport, a Harvard Medical School professor who specializes in mental health care in school settings. “For these kids, we need to intervene to support their learning deficits, otherwise treating them with stimulants will be a bust.”

The trickiest cases, Dr. Rapport adds, are really smart kids who have successfully compensated for their learning disabilities for years, by working extra hard. “They’ve been able to hide their weakness until they get older and there’s just too much heavy lifting. They’re often diagnosed with ADHD or depression unless someone catches the learning problem.

2. Repetitive distressing thoughts

The common diagnosis: PTSD

Intrusive thoughts and memories that a child can’t control are one of the key symptoms of PTSD. Clinicians think of PTSD as a damaged “fight or flight” response in a child who has had a disturbing experience, whether it was an upsetting event or a pattern of domestic violence or abuse. The experience is in the past, but the child keeps reliving the anxiety.

This can take place in the form of flashbacks, thinking about the event over and over, or be experiencing frightening thoughts that get “stuck.”

Other possibilities:

OCD:

“In both OCD and PTSD, you can experience thoughts that intrude, thoughts that you don’t want to be thinking about,” said Dr. Howard. “These thoughts come into your head, without your volition, and without your control. In both cases, they cause you distress, and you have to work to manage them.” But there is a major difference between the repetitive thoughts in OCD and PTSD, Dr. Howard notes: “With OCD it will be a concept the causes you distress, but with PSTD it’s an actual memory of something that happened.”

3. Restricted speech

The common diagnosis: Autism

Autism is a developmental disorder that causes a child to have impairments in communication. Children with autism may have a delay in (or complete lack of) the development of spoken language. The most obvious signs of autism are usually noticed between 2 and 3 years of age. Although many children on the spectrum do speak, they may use language in unusual ways, avoid eye contact, and prefer to be alone. Autism may first be noticed by school professionals, who become aware that the child is not interacting socially with his peers in an appropriate way.

Related: Why Autism Diagnoses Are Often Delayed

Other Possibilities:

Selective Mutism:

Selective mutism is an anxiety disorder in which children do not speak in particular social situations. Many children with selective mutism are talkative at home, but there may be a complete lack of speech in other settings, such as in school. They may not communicate with peers or teachers at all, which can lead to school professionals being concerned about their social development. These social difficulties may lead some school personnel to jump to the conclusion that they are on the autism spectrum.

“You can have difficulty with communication for a lot of reasons,” notes Dr. Kurtz. “The thing to look for is the consistency across situations. Kids with SM will be quite social and quite fabulous chatterboxes in some settings, otherwise, they probably don’t have SM.”

When it comes to making a diagnosis, it is important to make the distinction between a skills deficit and a performance deficit. Children with selective mutism have a performance deficit because they have the ability to speak but cannot demonstrate it in every setting, while children on the spectrum have skills deficits, so can’t demonstrate certain skills regardless of the setting.

Children with selective mutism may also display other symptoms that may lead to alarm bells being sounded for autism. Some kids with SM appear very “shut down” in their effect. “Because the kid’s trying, whether he knows it or not, to convince people to back off, he’s also going to have poor eye contact like a kid on the spectrum, flat affect like a kid on the spectrum,” said Dr. Kurtz. “He’s not going to look like a kid whose only issue is that he is stuck in terms of being able to talk.”

4. Sadness, fatigue, and difficulties thinking clearly

The common diagnosis: Depression

It is easy for most people to recognize the symptoms of depression: feelings of sadness decreased interest in usually pleasurable activities, fatigue, weight changes, and difficulty concentrating. While it is normal for everyone to feel “down in the dumps” sometimes, children experiencing sadness or irritability that lasts for more than two weeks and impairs their ability to function may be thought of as experiencing a depressive episode.

Other Possibilities:

Hypothyroidism:

Hypothyroidism happens when your thyroid (a gland in your neck) is not secreting enough of certain important hormones. The symptoms of hypothyroidism look very similar to those of depression and include fatigue, weight gain, feelings of sadness, and difficulty thinking clearly. However, the treatment for hypothyroidism is very different: children with hypothyroidism are treated using a thyroid replacement hormone.

Anxiety Disorder:

Certain anxiety disorders, such as OCD, can be extremely impairing and scary to the person experiencing them. Children with OCD can have obsessions about invoking harm to their loved ones, as well as other violent or sexual images. While these obsessions are not true to what the child actually wants to happen, he has difficulty getting them out of his head. There are times when depressed mood is what is noticed

first, but it may be secondary to another condition such as OCD. Due to the shameful thoughts that many children with OCD have, they may not feel comfortable sharing many of them and may get misdiagnosed with depression

.