Toddler speech delays and temper tantrums have long been assumed to go hand in hand, but no large-scale research had successfully backed up that assumption with data.

Until now.

A new, 2,000-participant study from Northwestern University found that toddlers with fewer spoken words have more frequent and severe temper tantrums than their peers with typical language skills.

It is the first study to link toddlers' delayed vocabulary with severe temper tantrums, including children as young as 12 months old, which is much younger than many clinicians typically believe problematic behavior can be identified.

"We totally expect toddlers to have temper tantrums if they're tired or frustrated, and most parents know a tantrum when they see it," said co-principal investigator Elizabeth Norton, an assistant professor in the department of communication sciences and disorders at Northwestern. "But not many parents know that certain kinds of frequent or severe tantrums can indicate risk for later mental health problems, such as anxiety, depression ADHD and behavior problems."

Similarly, both irritability and language delays are risk factors for later language and learning disorders, Norton said. About 40% of delayed talkers will go on to have persistent language problems that can affect their academic performance, Norton said. This is why assessing both language and mental health risk in tandem may accelerate earlier identification and intervention for early childhood disorders because children with this "double whammy" are likely to be higher risk.

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The study was published in the Journal of Applied Developmental Psychology.

"We knew from many other studies in older children that language problems and mental health problems occur together more frequently than would be expected, but we didn't know how early this relationship began," said Norton, also the director of the Language, Education and Reading Neuroscience (LEARN) Lab and a leader in the Institute for Innovations in Developmental Sciences (DevSci) at Northwestern.

The study surveyed more than 2,000 nationally representative parents who had a toddler between the ages of 12 and 38 months. Parents answered questions about their children's number of spoken words and their tantrum behaviors, such as how often their child has a tantrum when they are tired versus when they are having fun.

In the study, a toddler is considered to be a "late talker" if they have fewer than 50 words or aren't putting words together by age 2. Late talkers are predisposed to have severe and/or frequent temper tantrums at nearly double the rate of their peers with typical language skills, the study found. The scientists categorize tantrums as "severe" if the toddler is regularly doing things like holding their breath, hitting or kicking during a tantrum. Toddlers who have these kinds of tantrums on a daily basis or more may need help promoting their self-control skills.

"All these behaviors must be understood within developmental context," said co-principal investigator Lauren Wakschlag, professor and vice chair in the department of medical social sciences at Northwestern University Feinberg School of Medicine and the DevSci director.

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"Parents should not overreact just because the child next door has more words or because their child had a day from 'The Wild Things' with many out-of-control tantrums," Wakschlag said. "The key reliable indicators of concern in both these domains is a persistent pattern of problems and/or delays. When these go hand in hand, they exacerbate each other and increase risk, partly because these problems interfere with healthy interactions with those around them."

The survey is the first phase of a bigger ongoing research project at Northwestern University called "When to Worry," which is funded by the National Institute of Mental Health. The next phase, currently in progress, includes a follow-up study of approximately 500 toddlers in Chicagoland who are typically developing and also those who are exhibiting irritable behavior and/or speech delays. The study will examine brain and behavioral development to pinpoint those indicators that will help distinguish transient delays from the onset of problems.

Parents and their toddlers will meet with the Northwestern scientists annually until children are 4.5 years old. It is unusual for these different disciplines (e.g. speech pathology and mental health) to come together like this to focus on the "whole child," Wakschlag said.

"Our DevSci Institute is specifically designed to push academics out of their traditional silos so that they can work most effectively to solve real-world problems using all the tools at hand," Wakschlag said.

"We want to take all the pieces of information we get about development and put them together to form a toolkit that pediatricians or even parents can use to understand when to worry about a given child, and know what is developmentally expected versus not, so that children can get intervention early, when it is most effective," Norton said. Brittany Manning, a Ph.D. student in Norton's lab, is the paper's first author. The study question came in part from Manning's work as a speech-language pathologist.

"I've had many conversations with parents and clinicians about concerning temper tantrums and late talking, but there was no research data on the topic I could point them to," Manning said.

Parents who have a toddler between the ages of 21 and 29 months old who is exhibiting speech delays may be eligible to be part of the When to Worry study. Read more information at the When to Worry study website.

This research also was funded by the National Institute of Deafness and Other Communication Disorders of the National Institutes of Health (grants R01MH107652 and R01DC016273).