The COVID-19 outbreak was declared a global public health emergency on January 30, 2020, by the World Health Organization,[1] which continues to have an impact worldwide to date. Since the implementation of epidemic prevention policies globally, isolation and uncertainty are taking a severe toll on children’s psychological health, exacerbating the long-ignored mental crisis. Given the susceptibility to environmental exposures among preschool children, their mental health could be negatively affected by the risk factors related to the lockdown, especially emotional and behavioral problems.[2] Emotional and behavioral problems include a wide range of atypical behavior deviating from social standards,[3] such as anxiety disorders, disruptive disorders, and oppositional defiant disorders,[4] which are common psychiatric disorders during early childhood.[5] However, most existing research focused on children and adolescents, neglecting preschool children. Comparison of the prevalence of emotional and behavioral problems among preschool children before and during the pandemic could scientifically and intuitively reveal the impact of the epidemic on children's emotional and behavioral health. Thus, it is essential to conduct a meta-analysis to estimate the prevalence of emotional and behavioral problems among preschool children during the outbreak, which is helpful to the intervention for emotional and behavioral problems.
Before the pandemic, the prevalence of emotional and behavioral problems among preschool children ranged from 6.9–14.7% in various countries.[6, 7] During the pervasive lockdown, evidence suggested that the prevalence significantly elevated in countries worldwide, reaching up to 73.6%.[8] The following risk factors could explain preschool children’s increased emotional and behavioral problems. Firstly, a long-term lack of outdoor exercise may lead to the decreased release of certain neurotransmitters,[9] such as low levels of dopamine, serotonin, and adrenaline.[10] The function of emotion regulation in the brain is then adversely affected.[11] Therefore, reduced movement behavior during the lockdown could trigger preschool children’s negative emotions through neural mechanisms.[12, 13] Secondly, caregivers’ perceived economic and parenting stress could induce insensitive parenting practices and negative family atmospheres.[14] Given the strong dependence of preschool children on the family environment, reduced parent-child closeness[15] and negative parenting attitudes may cause increased emotional and behavioral problems.[5] Thirdly, the developmental characteristics of preschool children could exacerbate the effect of the above factors. Children’s advanced cognitive functions are still developing; they may have difficulty monitoring their behavioral performance and regulating their emotions,[16] which could affect preschoolers’ social adjustment.[17] Consequently, preschool children are more susceptible to the external environment,[18] especially when faced with deviant stimuli. As such, exposure to adversity in early life could affect children’s brain structure and function,[19] particularly in emotion regulation.[20] Therefore, it is critical to pay attention to preschool children's emotional behavioral problems during the epidemic.
Moreover, emotional and behavioral problems in early childhood may lead to other severe consequences, specifically in social-emotional development and academic achievement. On the one hand, regarding social-emotional development, most children with emotional and behavioral problems were found to co-occur with language deficits.[21, 22] Developmental language disorders have an adverse impact on children’s communication skills,[23, 24] thereby negatively affecting their social adjustment and life satisfaction. As the vital interactors of preschool children, parents’ emotions and interaction patterns are also affected by children’s emotional and behavioral problems.[25] Besides, evidence suggested that emotional and behavioral problems could result in inappropriate self-esteem and self-concept,[26] which could predict antisocial personality, deliberate self-harm, and psychiatric problems in adulthood.[5] On the other hand, concerning academic achievement, numerous studies have shown that children with emotional and behavioral problems are at high risk of academic failure.[27, 28] The possible mechanism is children’s reduced attention to school work and school absence.[29] More seriously, it could lead to more unemployment, jobs held for a short time, lower job status and income, and other lifelong effects.[5] During the critical period of physical and psychological alternations, the negative consequences of emotional and behavioral problems are irreversible and have lifelong effects. Since recovery and inspiration plans for emotional and behavioral problems are under consideration,[30] specific and precise estimates of children’s emotional and behavioral problems during the pandemic are essential, especially for preschoolers.
A growing number of empirical studies have been conducted to examine the prevalence of emotional and behavioral problems among preschool children during the COVID-19 pandemic. However, the prevalence of emotional and behavioral problems reported in studies varied considerably, ranging from 9.3–73.6%.[8, 31] Nevertheless, a study has shown that changes in problematic behaviors and anxiety symptoms among preschoolers were not statistically significant between the pre-pandemic and post-pandemic.[23] It is clear that current findings on the prevalence of emotional and behavioral problems among preschool children are inconsistent.
Hence, there is a necessity to conduct a meta-analysis of the prevalence of emotional and behavioral problems among preschool children in the context of the COVID-19 pandemic. Currently, only one meta-analysis is conducted to integrate the prevalence of emotional and behavioral problems. However, the participants were focused on children and adolescents instead of preschool children. Additionally, the above study was performed before the COVID-19 pandemic.[32] It follows from the above that no meta-analysis of the prevalence of emotional and behavioral problems among preschool children during the outbreak has been undertaken.
Therefore, the current study aimed to estimate the pooled prevalence among preschool children aged six years and under during the COVID-19 pandemic, reflecting the psychological effect of COVID-19. Moreover, we also examined potential factors that may explain the heterogeneity between studies. As such, the findings of our studies help to understand the prevalence of emotional and behavioral problems among preschool children during the COVID-19 pandemic and provide more information for further intervention and recovery.