Delayed speech development or developmental language disorder (DLD)?

One child starts speaking late and by the age of five nobody remembers there was ever a problem. Another child starts out the same way, but the difficulty stays - it changes shape, moves into sentences, then into reading and into friendships at school. That second picture now has a name: developmental language disorder, or DLD. This article is about how the two differ and how to tell which one you are looking at.

If you are at an earlier stage and still wondering whether to see a speech therapist at all, start with delayed speech development - when to see a paediatric speech therapist. It covers the warning signs at each stage and what a first visit looks like. This article goes further: the question of telling a delay apart from a disorder arises once your child has been assessed or is already in therapy, and the question is no longer whether to go, but for how long and to what end.

Delay versus disorder - what actually differs

Delayed speech development describes a state: your child says less, and says it later, than would be expected at this stage. It describes where the child is now, not what will happen next. Developmental language disorder describes something else - a lasting difficulty in acquiring language that persists despite support, has no explanation in another known condition or disability, and genuinely interferes with everyday life.

So one term is not a milder version of the other. A delay is recognised from what you can observe today; a language disorder is recognised only once it is clear that the difficulty is lasting and affects the child's life. Many children with a late start never receive a DLD diagnosis, because their language simply catches up. Others receive one after a year or two of observation - and that does not mean the earlier assessment was wrong.

“Will my child grow out of it?” - what the research says

This comes up at almost every first appointment and deserves an honest answer: very often yes, but not always, and it cannot be settled in advance for any individual child.

In a large population study conducted in Australia, around 19% of two-year-olds were identified as late talkers. By the age of four, about 30% of them had still not caught up with their peers. In other words: roughly two in three children with a late start later fall within the typical range, but the remainder are not a rounding error - they are a substantial group of children who need support.

The second finding matters just as much, though it is less comfortable. Prediction at the level of an individual child performs poorly. Early language measures alone say little about where a child will be two years later. Combining the language picture with family history does somewhat better - in one study, a family history of language difficulties was a slightly stronger signal than the child's own late start. In that same study, some children who were average talkers at 20 months met the criteria for a language disorder at four.

It is also worth knowing that catching up can be incomplete. As a group, children with a history of late talking score somewhat lower on some language tasks in later years, and difficulties can resurface when reading and writing begin. That is not a reason for concern about every child, but it is a reason not to close the subject for good on the day your child starts building sentences.

Where the term DLD came from

For years the same phenomenon went by several names, in Poland and elsewhere: SLI (specific language impairment), developmental aphasia, and others. Different names in different consulting rooms meant that a parent with the same child heard one thing from a therapist, another at the counselling centre, and a third at school.

Between 2015 and 2016 an international panel of several dozen experts agreed on shared terminology in the CATALISE project. They adopted developmental language disorder (DLD) for language disorders with no known biomedical cause. SLI was judged too narrow, because it treated language in isolation from the other difficulties that often accompany it. Names referring to aphasia were discouraged, because they suggest a parallel with conditions acquired after brain injury in adults - a different clinical situation.

One change carries particular practical weight. Previously a diagnosis required a mismatch between language level and nonverbal ability - the child had to have „typical intelligence but weak language”. In the current framing, that mismatch is not a requirement. What counts is whether the language difficulty is marked, lasting, and interferes with everyday functioning. Co-occurring developmental difficulties, such as ADHD, do not rule the diagnosis out either.

How common DLD is

In a population study of five- and six-year-olds, language disorder with no known biomedical cause was identified in around 7% of children. In practice that is roughly two children in a typical first-year class. That is a lot - and it is one reason for having a single, recognisable name rather than several parallel ones.

What actually changes when the difficulty turns out to be lasting

The most important change is the time horizon. With a delay that resolves, the plan is measured in months and ends when the child catches up. With a lasting language disorder, support is planned in years and its aim shifts: it is no longer only about reaching the age norm, but about the child understanding instructions in class, coping with reading comprehension, and having the tools to talk with other children.

The second change concerns who works with the child. A lasting language difficulty rarely stays a matter for the speech therapy room alone - support with reading and writing and cooperation with the school usually join it. How that team works in practice is described in our article on how a speech therapist, a neurologopedist and an educational therapist divide the roles at the start of school.

The third change is the least obvious and concerns the parent. A diagnosis takes the label of „lazy” or „not paying attention” off the child, and takes the feeling of having missed something off the parent. A language difficulty of this kind does not come from screens, from bilingualism, or from too few books at bedtime.

The clinical name and the paperwork

Be prepared for a gap between what you hear in the consulting room and what you see on paper. Polish education law has no term corresponding to language disorders of unclear origin, so opinions and statements tend to describe the difficulties or use older labels. That is a matter of naming rather than a challenge to the diagnosis - but conversations with the counselling centre and the school go more smoothly when you know about it in advance.

When to book a consultation

Do not wait for another stage of observation if your child understands noticeably less than their age would suggest, if the difficulty persists despite time and support, or if it is starting to affect friendships and learning. In those situations a speech and language assessment in Gdańsk establishes not only what your child can say, but how to plan support over a longer horizon. What the appointment itself looks like and what to prepare is covered in our article on preparing for a speech and language assessment.

On a separate page we describe assessment and therapy for delayed speech development.

Sources

• Bishop et al. (2017): CATALISE phase 2 - terminology for language development problems
• RCSLT: summary of the CATALISE consensus
• Norbury et al. (2016): prevalence of language disorder in a population study
• Longitudinal study of late talkers from 20 months to 4 years
• RADLD: developmental language disorder (DLD) fact sheet
• Gacka (2022): SLI or DLD? Terminology and Polish education law