Infant colic, young children’s temperament and sleep in a population based longitudinal cohort study

Problematic infant fussing and crying, often called infant colic, is a well-known condition among parents, causing them stress and concern. Despite its commonness, the cause of colic is still debated, effective treatment is lacking and the criteria for defining it are vague. The occurrence varies in different studies depending on the criteria used, however a systematic review has shown a mean prevalence between 17 and 25% across the world [1]. Infant colic usually occurs in the infant’s second or third week of life [2], persists at a high level (117–133 min a day) during the first 6 weeks, and then gradually resolves in the third or fourth month [1]. The crying is often described as persistent and more than is normally expected [3]. It might be questioned what a normal amount of crying and fussing is, and mostly it is the parents’ experiences and tolerance that determines when the crying is perceived to exceed normal [3]. However, when crying and fussing exceeds 2–3 h a day, it will usually be characterized as more than normal, both by parents and health professionals [2]. The most common definition of infant colic is Wessel’s “rule of threes”: “the infant fusses or cries more than three hours a day, more than three days a week, and for more than three weeks, but is otherwise healthy” [4]. The “rule of threes” does not point to any specific cause of colic. Although there are many theories, there is currently no consensus on the cause in the literature. The most frequently described causes are gastrointestinal disorders, infant characteristics (personality), immaturity of the central nervous system, parent-child interaction, and an extreme degree of normal distress [5].

Infants’ sleep/wake patterns will settle during the first year of life. According to recommendations, 12–16 h per 24 h is considered to be a normal amount of sleep for infants from 4 months to 12 months [6, 7]. At 4 months, 60–70% of infants sleep continuously for at least 5 h during a regular night [8, 9]. Henderson, France [8] found that this also applied for most 2–3 months old infants. The majority of infants wake up during the night; however, problems first occur when infants signal parents upon wakening rather than resettling themselves [10]. Younger infants more often require parental intervention to return to sleep, than older. However, when 12 months old, some infants still need parents to intervene to get back to sleep [10]. St James-Roberts and Peachey [11] claim that, in most cases, sleeping problems in infancy involve a delay in ending night-time signalling behaviour (crying) and can sometimes be explained by looking at the parenting environment. Night-waking and signalling, in many cases, can be prevented with a limit-setting parenting style [5]. While infant colic is most prominent during the infant’s first 6 weeks, infant sleeping problems appear later in infancy [11].

The literature is not consistent about whether infants who cry a lot in the first weeks of life also tend to have sleeping problems. St James-Roberts [3] claims that, in most cases, infant crying and sleeping problems are distinct cases. However, there is evidence that for some infants, fussing and crying (colic), sleeping problems, and feeding difficulties occur together, and are described in the literature as infant regulatory problems [12, 13]. The concurrent appearance of such problems increases the load on the parents and is associated with future mental health concerns of the child [14], and is thus important to study further.

The research on long-term consequences that infant crying has for the child is sparse. Some evidence exist that shows excessive crying or infant colic increases the risk of mood and behavioural problems in pre-school and early school age [15‐17], while the associations between infant colic and children’s sleep across the first 5 years of life, as far as we know, remains to be studied. As knowledge on how infant colic is associated with temperament and sleep later in childhood is limited, these relationships warrant further studies. Health care providers would benefit from a greater understanding of how colic can impact the infants’ future development, which in turn should have consequences for the follow-up of young families in child health centres.

The overall aim of this study was to increase our knowledge of the characteristics of infants with a history of colic and to study how colic in infancy is associated with the development of child temperament and sleep behaviour over time. Such knowledge will enable early, targeted interventions to support parents and children and prevent possible negative consequences of colic. More specifically, the research questions are:

In this study, the prevalence of infant colic is 11.9%, lower than reported in a recent systematic review showing a mean prevalence between 17 and 25% [1]. Differences in reported prevalence of infant colic is often explained by ways of defining colic and how it is assessed, and whether parent-reported, diagnosed by health professionals or measured with valid instruments. In a systematic review, only four tools for colic assessment were obtained; they all had limitations and the need for developing new and valid scales was highlighted [21]. Thus, most studies rely on parent-reported data on colic which includes many sources of error. In MoBa, colic is assessed through one single recall question when the child is 6 months old, and the colic period is passed. It relies on the mothers’ perception of their infant’s behaviour, how they remember the past period, their knowledge on infant colic and whether they have received the diagnoses from a health professional. Mothers may over- or under-report colic, but their perceptions have been found to be reliable [22]. The fact that data on colic were collected after the colic period might partly explain why the prevalence is lower than expected. On the other hand, the recall period was short and a Swedish study showed that the memories of colic are vivid even 4 years after the colic period [23]. Thus, it is relevant to assume that parents will label it as colic when they define crying as a problem in the child’s first weeks. The parents’ subjective perceptions of what colic is relate to how colic is described in the literature with unsoothable bouts of crying and fussing interpreted as a sign of infant distress, which again causes parental frustration and stress [24]. The MoBa study does not contribute any criteria or explanation of colic to guide parents in reporting the condition but has listed the question in a series of questions on common illnesses during infancy. If parents did interpret their infants’ crying as colic or did not consider colic an illness, they may not have reported it, thereby explaining the rather low prevalence of colic in the study.

In this study, there are significant differences between the colic group and the non-colic group on all variables. At 6 months of age, infants with a history of colic are rated as fussier and more challenging (temperament), they present more sleeping problems, they are breastfed less, and the families visit the child health centre more often than the non-colic group. Given the big sample size in this study, small differences might be significant and thus, the results should be interpreted with caution. However, the results imply that, for some infants, fussing and crying (colic), sleeping problems, and possible feeding difficulties (lower incidence of mothers breast-feeding in the colic group) occur together, a triad described in the literature as infant regulatory problems [12, 13]. In a study by Cook, Mensah [12], more than 53% of the parents reported one regulatory problem at 1 month of age and 7.3% of the parents reported the whole triad of regulatory problems. For mothers reporting two problems occurring together, sleeping and crying-and-fussing were most frequently described (11.7%) [12]. A longitudinal study on infant regulation and child mental health concerns found that infants with severe regulatory problems have much greater odds of experiencing mental health concerns at 5 and 11 years [14].

The Norwegian MoBa study asserts that, when infant colic is reported, mothers also more frequently describe the appearance of other regulatory issues, like feeding difficulties and problems with sleep. However, we have not studied the prevalence of the problems occurring together or the severity of regulation problems. Instead, we have studied how having experienced one of these regulatory problems (infant colic) is related to child temperament and sleep over time. As a result, we see that the temperament of children with a history of infant colic is perceived as more challenging by their mothers from the age of 6 months until 5 years than those without colic. The biggest difference between the two groups, and maybe the most challenging period, appears when the child is 18 months. Several studies support the finding that infants with colic remain more temperamental during childhood [15‐17]. Studying the impact of colic on sleep behaviour from 6 months to 5 years, we found that the children with reported colic were more likely to sleep less than recommended and to have more frequent night awakenings. The odds for sleeping less than recommended were higher than the odds for more frequent night awakenings. However, other studies have shown that frequent night awakenings are correlated with parental perceptions of a sleep problem while sleep duration is not [25].

The literature debates whether infant colic and sleep problems are linked together or not [11], but there is growing evidence that infant regulatory problems can occur as a single problem or as multiple regulatory problems [26]. When they occur together in early infancy, the odds that they persist when the child is nearly a year old is found to be threefold [27]. In addition, multiple regulatory problems are found to predict dysregulated behaviour across childhood [28]. In our study, we have shown an association between infant colic and other regulatory problems, such as problems with sleep, at 6 months. Further, we have shown that children with a history of colic are perceived as having a more challenging temperament by their mothers and have higher odds of being perceived as having sleep problems across time. However, the differences between those with and without colic appear to be moderate to small over time (6 months to 5 years). In many cases, regulatory problems—especially if there is only one—are transient and there is evidence that if colic resolves as expected when the infants are 3–4 months old, then the adverse effects on child temperament and behaviour are limited [29]. Still, the evidence that multiple regulatory problems often appear together and persist over time underlines the need for awareness of symptoms and close follow-up of the families. Infant crying and sleeping problems are a frequent cause of help-seeking from parents. In our study, we have shown that mothers who report colic visit the child health centres significantly more frequently than those that do not report colic. Since parenting is regarded as having an influence on the infants’ regulatory problems [12, 27], interventions should target parents and support and educate them in handling infants’ regulatory adaptation before the problems settle. There is evidence that interventions targeting overall parenting are effective in helping children with regulatory problems and their parents [5, 12]. Reported effects are reduced parental frustration anxiety, reported amount of infant crying, more contact with health professionals and increased knowledge about crying [30]. As described, the differences between the groups in this study are significant, but also moderate to small over time. The clinical significance should be more thoroughly investigated in future studies, however, our findings support previous research that infants with colic or excessive crying, alone or together with other regulatory problems in early infancy, have an elevated risk of later regulatory problems [26‐28].

Whether infant colic should be termed a regulatory problem raises an important discussion. Is it colic itself or the most prominent symptom of colic, excessive crying and fussing, that could be labelled a regulatory problem? If colic is a regulatory problem, this points to an understanding of colic as a behavioural condition and extreme variant of normal crying which could be explained by some of the existing theories of infant colic, like infant personality, immaturity of the CNS, parent-child interaction, or a high degree of normal distress [5]. A well-known researcher on infant colic claims, “Colic may be best viewed as a clinical manifestation of normal emotional development, in which an infant has diminished capacity to regulate crying duration” [31]. However, this leaves out the theory of colic being a gastrointestinal disorder. The gastrointestinal causes of colic are often referred to as developmental lactose intolerance, altered gut microorganism, immaturity of the gut, increased motilin receptors, or cow milk hypersensitivity [32]. Yet, research has shown that gastrointestinal disturbances only apply to a minority (5%) of infants who cry excessively during the first months of life [5, 30]. Still, it is important to be aware that the term colic is used as a collective term for excessive infant crying and fussing. Thus, a thorough assessment of infants at the child health centres should always be performed when parents present worries about the infants’ amount of crying, both to rule out illness and tailor the interventions.

Our findings, based on large data, show that infant colic may appear together with other so-called regulatory problems, i.e., sleeping difficulties and problems with feeding. As excessive crying and fussing are the prominent symptoms of infant colic, colic in many cases can be viewed as a regulatory problem. It is important to be aware of and act upon symptoms of colic and other regulatory problems when we meet parents and infants in the child health centres to prevent adverse outcomes. Infants presenting with more than one regulatory problem should receive special attention because the risk of negative long-term effects increases by the number of regulatory problems. Small to moderate differences in temperamental difficulties and sleep-problems across time indicate that the challenging period of crying and fussing during the infants’ first months are moderately associated with later behavioural difficulties. However, this will depend on whether the problems persist beyond the colic period, whether the regulatory problems occur as single or multiple, and maybe most important, whether the parents get the proper support and guidance in their visits at the child health centres.