Crying in the first 12 months of life: A systematic review and meta-analysis of cross-country parent-reported data and modeling of the "cry curve"

Abstract

Crying is an ubiquitous communicative signal in infancy. This meta-analysis synthesizes data on parent-reported infant cry durations from 17 countries and 57 studies until infant age 12 months (N = 7580, 54% female from k = 44; majority White samples, where reported, k = 18), from studies before the end Sept. 2020. Most studies were conducted in the United States, the United Kingdom, and Canada (k = 32), and at the traditional cry "peak" (age 5-6 weeks), where the pooled estimate for cry and fuss duration was 126 mins (SD = 61), with high heterogeneity. Formal modeling of the meta-analytic data suggests that the duration of crying remains substantial in the first year of life, after an initial decline.

FIGURE 1

PRISMA flow diagram

FIGURE 2

(a) Global map presenting the number of available studies from each country. (b) Numbers of studies providing data per age interval and per country. (c) The number of studies conducted at each age interval, by questionnaire and diary measures

FIGURE 3

Distribution of gender across study samples. The relation between sample size and male to female proportion (gender balance). A gender balance of “0” indicates a male‐only sample, while a gender balance of 100 indicates a female‐only sample. The orange area represents the theoretical sampling error for a given sample size, obtained through simulations (n = 10,000 for sample sizes of 1, 5, 10, 25, 100, 200, 400, 700, with a true proportion of 50%, indicated by the red line). The orange shaded region represents the 5% and 95% quantiles of gender balance for a given sample size and the brown dots represent the available data

FIGURE 4

Weighted mean duration for three measures of infant cry duration: (a) cry/fuss; (b) cry only; (c) total distress. Each panel combines country‐level data across ages. Orange circles represent mean durations of individual samples within available studies. The circle size reflects the number of infants and is used to visualize that influence of a given sample in the calculation of the weighted means. The light orange bar represents the standard deviation of age intervals, pooled across available samples. The dark circles represent the weighted mean of each age interval, and the error bar represents its standard error

FIGURE 5

Weighted mean of parent‐reported cry/fuss duration across the infant age intervals and across all available countries (blank cells represent ages and countries with no available data). The standardized mean difference (SMD) is calculated by comparing the weighted mean of each cell to the overall weighted mean across age intervals and countries, providing an overview of the effect of both age and country on cry/fuss duration

FIGURE 6

(a, b) Inferred curve representing the change in cry duration across ages, modeled as a double exponential (a) and a change‐point detection (b), fitted using the posterior means of the inferred model parameters (solid curve), with uncertainty presented using 95% Credible intervals (shaded region around the curve), and data points (circles). (c) Posterior distribution of the cry peak, inferred from the double exponential model fitted to the meta‐analytic data. (d) Posterior distribution of A ₀, the asymptote of the double exponential model. It represents the inferred theoretical minimum value towards which cry duration decays. (e) Posterior distribution of the time of the change‐point between high and constant cry period and the exponential decay in the change point detection model. (f) Posterior distribution of A ₀, the asymptote of the change‐point detection model