Missing the Words: Why Developmental Language Disorder Often Goes Undiagnosed in Autistic Children
When a child struggles to speak, understand language, or follow conversations, most parents and providers know something is off. Language matters. It is how children connect, ask questions, show emotion, and eventually learn to advocate for themselves. But for many autistic children, those language difficulties are explained as “just part of autism” and nothing more. What often gets missed is a second condition that needs its own name and support: Developmental Language Disorder, or DLD.
Let’s look at the numbers. DLD affects about 1 in 14 children, which is about 7 percent of the population. That makes it one of the most common developmental conditions. It is more common than autism, ADHD, or dyslexia. That also means DLD does not just happen in kids without other diagnoses. Based on the numbers, we should expect that 1 in every 14 autistic children also has DLD. In reality, the overlap may be even higher, since many autistic children already show early language delays. But most of them are never given that second diagnosis. Their language challenges are included under the autism label, and the specific signs of DLD—like short sentences, poor grammar, or low vocabulary—get ignored.
Part of the reason this happens is because of how DLD is defined in diagnostic manuals. The DSM-5 and ICD-11 say DLD should only be diagnosed if the language problems are not better explained by another condition. This sounds logical on paper, but it causes problems. Once autism is diagnosed, many providers stop looking. They assume the language delay is fully explained by autism. But that is not always true. Autism usually affects social communication. This includes things like understanding tone, body language, or how to take turns in conversation. DLD affects the structure and use of spoken language. This includes vocabulary, sentence length, and how clearly someone speaks. These are different areas, even though they can both exist in the same child.
DLD also has clear clinical criteria. It is not diagnosed by guessing or just watching a child. A real DLD diagnosis comes from standardized testing, usually done by a speech-language pathologist (SLP). These tests measure how well a child understands and uses spoken language compared to other children their age. Some examples are the CELF-5, the PPVT, and the EVT. These are not just checklists. They are tested tools that show how far behind a child might be in vocabulary, sentence structure, or understanding. If a child scores low and other reasons like hearing loss or global delays are ruled out, then DLD should be diagnosed. Having autism should not cancel that process. In fact, it should make providers look even more closely.
As a parent, it can be frustrating to hear that your child has “Level 2 autism” or “Level 3 autism” and not know what that really means. You might be told your child has a lot of support needs, but not get much explanation about their language skills or learning profile. If your child has both autism and DLD, that is two areas of need. Leaving one of them out means your child may be treated as more limited than they really are. And it may delay services that could help, like targeted speech therapy or extra support in school.
It also affects how we understand autism overall. Some children are called “profoundly autistic” because they do not speak or have very limited language. But in many cases, that may be a mix of autism and DLD. Not being able to speak does not always mean someone has a more severe form of autism. It may mean they also have a separate language disorder that was never named. And that difference matters. When we recognize both conditions, we can give more tailored support and open the door to better outcomes.
Clinicians need the freedom to name what they see. Autism and DLD can exist together. Ignoring one of them does not help the child. It only makes it harder for families to get the support they need. Parents deserve real answers. Children deserve full evaluations. And professionals need to be able to look beyond one label and see the whole picture.
