Language Regression in Children: Why It Happens and When to Act

Temporary regression: stress, illness, and transitions

Children sometimes temporarily regress in language — and in other skills like toilet training or sleep — when facing significant stress or change. Common triggers include a new sibling, starting daycare, a family move, an illness, or a disruption in the household. In these cases, the regression tends to be mild, short-lived, and accompanied by the child otherwise seeming well and engaged. The child usually regains their prior skills within a few weeks as they adjust. This type of regression, while concerning to parents, is generally not a sign of an underlying developmental problem — but it should still be mentioned to the child's provider 1Ref 1American Academy of Pediatrics, Council on Children with Disabilities (2020).Promoting Optimal Development: Identifying Infants and Young Children With Developmental Disorders Through Developmental Surveillance and Screening.AAP statement that regression (loss of previously acquired skills) at any age warrants prompt evaluation rather than watchful waiting.

When regression is more concerning

Regression becomes more medically concerning when: it is significant (losing many words or stopping talking almost entirely); it is not tied to an obvious stressor; it persists beyond a few weeks; it is accompanied by other changes like loss of social interest, decreased eye contact, changes in play, or behavioral shifts; or it occurs after an illness, particularly a high fever or seizure 1Ref 1American Academy of Pediatrics, Council on Children with Disabilities (2020).Promoting Optimal Development: Identifying Infants and Young Children With Developmental Disorders Through Developmental Surveillance and Screening.AAP statement that regression (loss of previously acquired skills) at any age warrants prompt evaluation rather than watchful waiting5Ref 5Centers for Disease Control and Prevention (2024).Learn the Signs. Act Early..CDC guidance that loss of any skill previously acquired at any age is a red flag warranting prompt evaluation, not a wait-and-see approach. Any of these patterns warrants prompt evaluation rather than watchful waiting.

Regression and autism spectrum disorder

One well-recognized pattern in autism spectrum disorder is language regression — typically occurring between 15 and 30 months, when a child who was developing language seemingly on track suddenly loses words or phrases 2Ref 2Pickles A, Simonoff E, Conti-Ramsden G, et al. (2009).Loss of language in early development of autism and specific language impairment.Language regression in autism typically occurs between 15 and 30 months; approximately one-third of children with ASD experience a regressive pattern3Ref 3Meilleur AA, Fombonne E (2009).Developmental regression in autism spectrum disorders.Average age of regression in ASD is around 20 months; most children who regress showed subtle earlier differences; social withdrawal and loss of eye contact accompany language loss. Studies estimate that approximately one-third of children with ASD experience this regressive pattern, with an average age of regression around 20 months 3Ref 3Meilleur AA, Fombonne E (2009).Developmental regression in autism spectrum disorders.Average age of regression in ASD is around 20 months; most children who regress showed subtle earlier differences; social withdrawal and loss of eye contact accompany language loss. Research also notes that most children who regress showed subtle earlier developmental differences before the regression became apparent 3Ref 3Meilleur AA, Fombonne E (2009).Developmental regression in autism spectrum disorders.Average age of regression in ASD is around 20 months; most children who regress showed subtle earlier differences; social withdrawal and loss of eye contact accompany language loss.

The regression itself does not establish a diagnosis of autism; a full developmental evaluation is needed. But when regression occurs in this age window alongside changes in social engagement, it typically prompts evaluation with particular attention to autism.

Medical causes of language regression

Beyond developmental causes, there are medical conditions that can cause language regression and require their own workup. Landau-Kleffner syndrome (acquired epileptic aphasia) is a rare childhood-onset condition in which loss of language occurs in the context of epileptiform EEG activity during sleep 4Ref 4Smith MC, Hoeppner TJ (2003).Epileptic encephalopathy of late childhood: Landau-Kleffner syndrome and the syndrome of continuous spikes and waves during slow-wave sleep.Landau-Kleffner syndrome (acquired epileptic aphasia): rare cause of language regression in children, characterized by loss of language in the context of epileptiform EEG activity during sleep. Other epileptic encephalopathies, metabolic conditions, and neurological disorders can also cause regression. When regression occurs alongside any neurological symptoms — unusual movements, seizures, behavioral changes, or changes in coordination — a medical evaluation including neurology may be warranted alongside the developmental assessment 1Ref 1American Academy of Pediatrics, Council on Children with Disabilities (2020).Promoting Optimal Development: Identifying Infants and Young Children With Developmental Disorders Through Developmental Surveillance and Screening.AAP statement that regression (loss of previously acquired skills) at any age warrants prompt evaluation rather than watchful waiting.

What evaluation involves

A child with language regression should be seen by a pediatrician promptly 1Ref 1American Academy of Pediatrics, Council on Children with Disabilities (2020).Promoting Optimal Development: Identifying Infants and Young Children With Developmental Disorders Through Developmental Surveillance and Screening.AAP statement that regression (loss of previously acquired skills) at any age warrants prompt evaluation rather than watchful waiting5Ref 5Centers for Disease Control and Prevention (2024).Learn the Signs. Act Early..CDC guidance that loss of any skill previously acquired at any age is a red flag warranting prompt evaluation, not a wait-and-see approach. Depending on what is found, referrals may follow to a speech-language pathologist, a developmental pediatrician, a neurologist, or a combination. The evaluation will try to establish the timeline of the regression, what skills were lost and what remains, and whether there are associated developmental, behavioral, or neurological features. A hearing test is almost always part of the workup. For children under 3, referral to early intervention can run simultaneously with the diagnostic evaluation and does not have to wait for a diagnosis.