Statistical analysis
irritability/aggressiveness
REGRESSION
The main exposures were the initiation of breastfeeding and the durations of ABF and PBF. The outcome was the child’s clinical presentation severity defined by a set of variables (ADOS-2 CSS, VABS-II standard scores in communication, socialisation and daily living skills, IQ, SRS-2 T-total score and ABC scores for irritability/aggressiveness, lethargy/social withdrawal, stereotyped behaviours/self-harm and hyperactivity/lack of cooperation). In our analysis, we took into account multiple confounding factors considered in previous studies on the association between breastfeeding and children's cognitive developmentContinuous variables are described by means ± SDs or medians with interquartile ranges (IQRs) and categorical variables by frequencies and percentages. The Chi-square or Fisher's test and the Wilcoxon Mann–Whitney test or ANOVA were used, as appropriate, to compare differences between children: breastfed or never, included in the study or not, with or without missing data for confounders.We evaluated associations of (i) the initiation of breastfeeding and (ii) the durations of ABF and PBF among breastfed children on clinical severity outcomes using ANOVA and Spearman’s correlations respectively. When the p-value of the effect was < 0.20, a multiple linear regression analysis adjusted for the confounding variables listed above was computed. The chained equations missing data method