I’ve written about infant crying, particularly the nebulous entity known as colic, a few times on SBM. It’s a subject of special interest to me, not just because I am a pediatrician but because I find the psychology behind our varied interpretations of a baby’s cry and the range of our responses to it fascinating. Infant crying, typically when interpreted as “fussiness”, is also a gateway for many families into the world of irregular medicine, which is my thing that I say.
Earlier this week, as Syrian children were being murdered with chemical weapons and (insert Trump reference), many journalists were furiously describing the results of a new study on infant crying and the prevalence of colic in different countries:
- “Canadian Babies Cry the Most, Study Says“
- “Canada tops list of countries with most crybabies“
- “Babies cry more in UK, Canada and Italy, less in Germany, study finds“
- “Babies in Britain, Canada and Italy cry more than elsewhere – study“
- “Want the baby to stop crying? Be Danish. Don’t breastfeed“
And a press release from the University of Warwick, where the study originated, made some bold claims:
Babies cry more in Britain, Canada, Italy and Netherlands than in other countries – proved for first time by new research by the University of Warwick.
Psychologists have created world’s first universal charts for normal amount of crying in babies during first three months
In Denmark, Germany and Japan, parents deal with the least amount of crying and fussing
Trust me, I could go on. Not unexpectedly, none of the reports of the study’s findings got it right. Some were worse than others of course, but they all seemed to ultimately miss the point of the study. They were distracted by the bright shiny object, the sexy but inaccurate claim that babies in a particular country or three cry more than babies in other countries around the world. But that isn’t really what the study found.
But don’t take my word for it. Here is a link to the entire study. No relying on an abstract, a press release, or a couple of the study author’s quotes in hyperbolic news articles this time!
The study specifics
In the study, which is “a systematic review and meta-analysis of fuss/cry durations reported in diary studies from around the world,” the researchers set out to document with improved accuracy the changes in crying that takes place over the first 12 weeks of life. Based on smaller and inconsistent prior studies, according to the authors, we tend to expect crying to gradually increase over the first few weeks of life, peak at 5-6 weeks, and then begin to decrease. By looking at data from multiple countries, they wanted to see if a “universal crying curve” exists.
In addition to average fuss/cry time in different countries, they wanted to see if how a baby is fed plays a role and also to quantify the prevalence of colic in different countries at different ages during the first 3 months of life. Although not stated explicitly as a goal of the study, they also appear to have set out to come up with a percentile chart that might be used clinically to help determine if a baby is crying too much and needs evaluation. This idea would never work, and the fact that they came up with the concept really is not surprising considering that none of the study authors actually take care of infant patients. The lead author is a psychologist at the University of Warwick.
Inclusion criteria required that each study in the analysis must be observation only, include at least one 24-hour cry/fuss diary, involve only an unselected population of infants between 1 and 13 weeks, and report or have average cry/fuss durations and distribution indices available. In order to analyse data on colic prevalence, only studies with at least three 24-hours cry/fuss diaries were used. This is because they strictly adhered to the modified Wessel criteria for colic, which require an infant to cry for more than three hours a day for three days in a one-week period. This is already enough to make their colic data fairly questionable.
They also used a metric to determine the quality of each included study which is too cumbersome to get into, but it’s in the paper and pretty standard. And as previously stated, their major outcome measure was average total cry/fuss duration over 24 hours at different ages in the first 3 months. Specifically, they looked at 1-2 weeks, 3-4 weeks, 5-6 weeks, 8-9 weeks, and 10-12 weeks.
Their systematic literature search came up with 4,109 articles for possible inclusion, and after what sounds like a lot of work they determined that only 28 met their criteria. But because some of the articles included multiple population samples, they actually were able to analyze 33 distinct groups of infants. So right off the bat we aren’t talking about a huge number, but it isn’t insignificant. That isn’t my main concern with the interpretations however.
What did the study analysis reveal?
First, we’ll look at average crying overall. They found that average fuss/cry time over the first six weeks of life was 117-133 minutes, and that this was consistent at 1-2 weeks, 3-4 weeks, and 5-6 weeks. So the idea that crying gradually builds to a peak at 6 weeks appears to be inaccurate. This was followed by a decent decrease in crying at 8-9 weeks, and then again at 10-12 weeks when crying averages were about half what they were in the first 6 weeks of life. This jibes with the common understanding that colic tends to resolve by 3-4 months.
As we would expect based on the above data, the prevalence of colic followed a similar pattern. There was a solid significant difference between the percent of babies assigned the label of colic at 10-12 weeks (0.6%) and all of the other time periods. The peak of colic, again not surprising anyone, occurred at 5-6 weeks with a prevalence of 25.1%. This also jibes with the common understanding that colic tends to ramp up at roughly 3 weeks and that about a third of babies end up being assigned the “diagnosis.”
As trumpeted by the media, when the authors took country of origin into account they found a few interesting outliers in average crying time and the prevalence of colic, but only one that I think is meaningful. And it wasn’t Canada.
German babies, bless their hearts, were found to have statistically less crying averages at 1-2 weeks and at 3-4 weeks compared to the overall average, crying about a half hour less each day. Japanese infants cried a bit less each day at the 5-6 week mark. Infants in Denmark, where little ones are left in strollers outside restaurants while their parents dine, appear to cry less at every time period except 8-9 weeks, and cry about an hour less per day at 5-6 weeks. What the media latched onto was the finding that infants in Canada had crying times greater than the overall average at 3-4 weeks and that infants in The Netherlands cried more at 5-6 weeks.
When it comes to colic, the study found that UK babies had a significantly higher prevalence at 1-2 weeks. The media’s exaggerated claims aside, Canadian babies were only found to have more colic at 3-4 weeks while Italian infants were significantly above average at 8-9 weeks. Babies in Denmark and Germany were found to have significantly less colic at 3-4 weeks. All included countries had equivalent crying at 5-6 weeks.
Feeding type was also looked at as a possible variable in the amount of overall crying and the prevalence of colic, and there were some significant findings. Although not likely to be included as part of the breastfeeding support provided by many lactation consultants, and certainly not in any “baby-friendly” initiatives (but I won’t name any names), bottle-fed babies were found to have significantly less crying at 3-4 weeks onward and less colic at 5-6 weeks. The media largely ignored this aspect of the study, however.
What’s wrong with the study?
There are a lot of limitations to this research. A lot. First off, the studies involved subjective parental assessments of infant crying. As I’ve written about before, how a parent quantifies how much time their baby cries can be significantly impacted by stress and fatigue as well as by personal and cultural expectation. This study was working with a very limited number of crying diaries and doing a lot of extrapolating.
Their strict use of modified Wessel criteria to diagnose colic may be convenient, but it almost certainly leads to an inaccurate estimation of how many infants acquire the label in the real world. In practice, pediatricians and family doctors don’t really have parents keep crying diaries and then strictly follow any criteria. They just ask generally how much a baby cries, perhaps after mentioning the rule of 3’s.
Parents who have sought medical attention out of concern that their baby cries for an excessive amount of time are more likely to be tired and anxious, and to overestimate the amount of time that their child spends wailing. The perception of crying intensity and duration is also affected by expectations of what is normal, something that is extremely variable as well. Most pediatricians don’t really worry about labels like colic, although they may mention it during discussions with caregivers, and focus more on ruling out pathology and reassurance. To the author’s credit, although they mention the possibility that their findings reveal a genetic or biological difference between babies from different countries, they state that any real differences are more likely to be cultural. They do not, unfortunately, mention that all of these findings may simply be random noise in the data.
The most glaring limitation, considering how this study was reported by the media and the University of Warwick’s press release, is that it in no way represents an assessment of crying patterns in babies around the world. It included samples from very few countries, so few in fact that I will just list them: the UK (10 samples), Canada (6 samples), the United States (5 samples), Italy (2 samples), The Netherlands (1 sample), Germany (4 samples), Australia (1 sample), Denmark (3 samples), and Japan (1 sample).
That’s it. Japan was the only Asian representative. Australia had one sample which wasn’t even included in the colic data. The Netherlands had one as well. No data came from developing countries. Nothing from Africa, Central or South America, Eastern Europe, India, etc., etc. To makes claims that this data represents crying around the world is more than simple exaggeration. It’s dishonest. To be clear however, the authors point this out adequately in the paper. It is the media and University press release that are at fault. Even within the represented countries it is a stretch to make any confident claims.
What does it all mean?
So at the end of the day, what does this study really add to our understanding of infant crying and colic? Not much, and definitely not what the many news articles seem to think it does.
Based on this study, it appears that crying doesn’t gradually increase over the first few weeks of life. Babies on average just tend to cry a lot until a point, likely some key period of neurological development, when they begin to gradually cry less and less. This isn’t really earth shattering new information, but it’s at least something.
All the stuff about different rates of crying and colic in various countries is probably noise. The exception, maybe, is Denmark. Based on this study, as limited as it is in worldliness and documentation, babies in Denmark appear to either cry less, or are perceived to cry less by caregivers, than in the other included countries. If real, this is very likely related to a general cultural approach to parenting and unique expectations regarding infant crying. But to an unbiased observer taking objective daily measurements of crying over the first 12 weeks of life, the children in all of these countries probably cry about the same average amount.
But perception is reality when it comes to crying. It doesn’t matter if a particular baby actually cries a lot or if caregivers just think that they do. They still need to be evaluated for pathology and, if the baby is healthy, the parents need education and reassurance. So the study authors were absolutely correct when they wrote that “further analysis of caretaking patterns may prove to provide clues for effective preventative strategies.”
In regards to the role of different feeding types in crying and colic, this new data supports some earlier studies showing increased crying and more challenging temperaments in breastfed babies during the first six weeks of life. This effect is likely real but minimal in most babies. I certainly wouldn’t use this new paper as a reason to recommend against breastfeeding, but it is definitely one of many reasons to be supportive of mothers who do choose to feed their babies formula.
Are there any clinical implications from this study?
No, not really. Based on the data from the study, the authors put together a percentile chart for minutes spent crying each day at different ages during the first 3 months. It’s like the charts pediatricians use to plot weight, length, and head circumference in young infants to follow over time and help them pick up on any concerning trends in growth. The study authors offer this up as a potential clinical tool to help reassure caregivers.
While I appreciate their good intentions, thinking for one minute that a chart like this might be clinically useful reveals their lack of clinical experience. You can’t use a chart like this for such a subjective experience. It would be like making a percentile chart for cough…or nausea. What we know about infant crying epidemiology, even with the addition of this study, is still limited. Does gestational age matter, to give just one example. Should there be different charts for breast versus formula fed babies? Should I worry more if a baby from Denmark is at the 90th percentile than if it’s a Canadian child?
If a parent is worried about their child’s crying, an assessment is mandatory. This requires a thorough history and physical exam. Sure there are many examples of serious pathology that result in excessive crying, although typically it’s of the sudden onset variety rather than the chronic crying we think of with colic, but plenty of bad things don’t. I could never simply reassure a parent based on the fact that they their child’s crying isn’t above the 90th percentile. And if the assessment is reassuring, crying above some arbitrary cutoff wouldn’t change my management.
Conclusion: Don’t cry over bagged milk?
It is important to always remain skeptical when reading news reports and press releases about recently published studies. The media often will pick out one small but sexy aspect of a study and run with it, perhaps because of journalistic/intellectual laziness, a lack of critical thinking skills, or a poor understanding of how to interpret scientific research. Or perhaps because a desire for more clicks has biased their judgement. Many probably just assumed that a university press release was trustworthy.
In this case, a lot of likely well-meaning journalists, for whatever reason, followed a false lead and reported an exaggerated version of a minor finding of this study. Babies don’t cry more in Canada than in the rest of the world. At most we can say that babies in Denmark may cry less than in some other countries, but even that is likely the wrong conclusion. Parents in Denmark likely just don’t worry about crying as much as in some other countries.
The good news, and this was absolutely confirmed by the study in question, is that after 6 weeks of life the amount of average daily crying begins to decrease. And by 3 months of age very few babies will be perceived as crying excessively by caregivers. There is a light at the end of the tunnel. Our job as medical providers who work with worried parents is to provide reassurance when appropriate, and education that may help either reduce the total amount of crying, or at least improve the perception and tolerance of it.