The Relation of Crying to SBS

Author: Marilyn Barr, Founder/Former Executive Director, NCSBS

As you may have read in the section about Shaken Baby Syndrome (SBS), frustration with an infant’s crying is the most common reason someone shakes a baby. You may wonder how we know this?

brazelton curve

It all started in 1962, when Dr. T. Berry Brazelton, a renowned pediatrician and child development researcher, conducted a study of normal healthy infants by asking their parents some questions about their infant’s crying routine. In this study Dr. Brazelton found that all infants went through a stage in their development where they cried increasingly more. This crying began at about 2 weeks, peaked around six weeks of age and began decreasing around 12-16 weeks (3-4 months of age).

Twenty-four years later in 1986, two other pediatric developmental pediatricians, Dr. Urs Hunziker and Dr. Ronald Barr replicated Dr. Brazelton’s study. Their research of normal healthy infants in Montreal, Canada found the exact same results as Dr. Brazelton had. There have been several other studies done since that validate this normal crying curve of infants in the first few months of age.

This is an important discovery because the assumption for years was that if your baby cried excessively they had "Colic"" leading parents and caregivers to believe there was something wrong or abnormal with their baby. Extensive research now tells us that all infants go through a stage of increased crying, although some may cry a lot more than others. This crying is not an indication that there is something wrong with the baby but rather a normal developmental stage in all babies lives. You’ll notice on the simplified graph to the right that the crying starts to increase at about 2 weeks of age, peaks in the second month of life and then gets less at about 4-5 months. It is very important to remember that all babies go through this but some cry a lot, 5 or more hours, and some far less, only 30 minutes in a day/night.

So, the question remains, how do we know crying is the reason a person becomes so frustrated that they shake an infant? Certainly, we know that many have confessed after they shook their infant saying things like “I just could not stand the crying anymore", or “He would not stop crying so I shook him.” Cases like these are an indication that frustration with crying is certainly a reason someone shakes an infant, but is it the primary reason?

In order to scientifically show that this frustrating crying parents talk about has a very important affect on the possibility that a parent or caregiver could end up shaking an infant; we needed to prove that the incidence (occurrence) of hospitalized cases of SBS victims resembled a curve much like that of the crying curve. That is to say, that it would begin to go up in the first few weeks, be the most at about 2 months and then go down.

california curve

This is just what happened in a study conducted in 2006 by Dr. Ronald Barr and Dr. Roger Trent. They looked at 273 diagnosed cases of SBS in the California reporting data base. They found that the number of hospitalized cases of SBS definitely did follow the exact same curve as the crying curve. If you look above at the “infant crying curve” and to the right for the incidence of SBS cases curve” you will see they are alike. This gave us the evidence that infants who are shaken in the first few months of life are likely the result of a parent or caregiver becoming frustrated with the infants crying. However, Dr. Barr knew that in the California cases it was not possible to find out how many of the caretakers/parents actually stated that it was the crying that made them so angry at the baby, because California did not keep these kinds of records.

So, Dr. Barr’s next study took this a step further. Using the National Center on Shaken Baby Syndrome Victims Database, which at that time was a gathering of 757 reported cases of SBS, Dr. Barr looked at the pattern of the ages at which Shaken Baby Syndrome occurred, which included 591 cases that had no stated reason for the shaking and 166 cases that stated crying as the reason for shaking. And as you can see in the graph on the right or above, regardless of what the stimulus (reason) might have been, the shape of the curves is virtually identical to that of the crying curve and that of the reported cases in California, as is the red line that shows the cases where the person stated the reason they shook the baby was due to the crying.

victims database crying curve.png

The significance of these two studies is very important because they both compare the crying curve, which all infants go through, to the incidence (number) of shaking episodes. And in the comparison of the two curves, in both cases, the age at which cases of SBS are reported and hospitalized follows the exact same shape as the crying curve, regardless of whether a reason for the shaking was indicated. This certainly shows that frustration with an infant’s crying is definitely related to the number of shaken baby cases.

This means there is a unique opportunity to prevent SBS by providing a prevention program that goes beyond simple warnings to not shake an infant and rather address the main cause of the shaking, frustration with a baby’s crying. If parents and caretakers understand that this time in a baby’s life is a completely normal phase in their development, we can provide steps to cope with this crying. Encourage caretakers and parents to walk away from the baby when they are very frustrated. And help them understand the dangers of shaking a baby when they become so frustrated with the baby’s crying.

“There is a unique opportunity to prevent SBS by providing a prevention program that goes
beyond simple warnings to not shake an infant and rather address the main cause
of the shaking, frustration with a baby’s crying.”

This may reduce the likelihood that someone caring for an infant would react to their frustration with the babies crying by shaking them. The prevention program the Period of PURPLE Crying is the program we have developed to address all these situations. It is being given to parents and caretakers throughout North America.