Abstract: Despite of the differences in symptomology, externalizing and internalizing problems often co-occur among children and adolescence. As the concurrent and longitudinal associations between externalizing and internalizing problems are well documented in the literature, externalizing-internalizing co-occurrence has been an established psychopathological phenomenon, and has become an important perspective in studying children and adolescent psychopathological problems. The current article reviewed the extant findings with regard to the prevalence and development of externalizing-internalizing co-occurrence, and its developmental outcomes and the underlying factors and mechanisms. With regard to the prevalence of the co-occurrence of externalizing and internalizing problems, previous studies demonstrated that 1.4% - 2.2% of children and 7% adolescence fall into the externalizing-internalizing co-occurrence subgroup. As to the development of externalizing-internalizing co-occurrence, researcher investigated the development of the co-occurrence status, as well as the co-development of externalizing and internalizing problems. Researchers reported both stability and change of co-occurrence status. Specifically, 18% - 44% of the externalizing-internalizing co-occurred children and adolescents stayed in this subgroup over time. Most of the children and adolescents of co-occurrence subgroup came from the prior pure externalizing subgroup, and developed into pure internalizing group. Among all the psychopathology subgroups, the co-occurrence subgroup had the smallest likelihood to transit into the normal group. In terms of the co-development of externalizing and internalizing problems, researchers reported a subgroup consisted of 3.2% - 3.7% of children and adolescents that characterized by chronically high trajectories of both externalizing and internalizing problems. Developmental change of co-occurrence was also evident, as another typical co-development trajectories is characterized by decreases in both externalizing and internalizing problems through development. The co-occurrence of externalizing and internalizing problems is also distinct from the occurrence of a single problem. As demonstrated by prior studies, children with co-occurred externalizing and internalizing problems would have impaired social relationships with peers in adolescence. For the adolescents, they might suffer severe psychosocial problems later in late adolescence or adulthood, such as suicide, crime, and mental disorders. Turning to the reasons underlying externalizing-internalizing co-occurrence, previous studies revealed multiple individual and contextual factors that set it up. Specifically, boys are at higher risks of having the co-occurrence, though the development of co-occurrence did not show much gender difference. Studies have consistently shown that the temperament of negative emotionality is strongly related to externalizing-internalizing co-occurrence. Negative parenting practices and adverse peer relations, such as abuse, psychological control, school bullying, constitute important contextual risk factors of externalizing-internalizing co-occurrence. From the perspective of developmental cascade, researchers also deposited that the co-occurrence is resulted from a developmental process that one problem lead to another. Considering limitations of the literature, future studies regarding externalizing-internalizing co-occurrence can be advanced with two theoretical frameworks. The first is developmental cascade, by which the future researchers can systematically investigate the developmental path of genetic, neural, temperamental factors leading to externalizing-internalizing co-occurrence. The second is the interaction between multiple individual factors and contextual factors, which allows future studies to reveal the contributions of the factors of different levels and domains. The employment of the two frameworks would lead to more systematic and holistic understanding of co-occurrence of externalizing and internalizing problems among children and adolescence. With regard to the prevalence of the co-occurrence of externalizing and internalizing problems, previous studies demonstrated that 1.4% - 2.2% of children and 7% adolescence fall into the externalizing-internalizing co-occurrence subgroup. As to the development of externalizing-internalizing co-occurrence, researcher investigated the development of the co-occurrence status, as well as the co-development of externalizing and internalizing problems. Researchers reported both stability and change of co-occurrence status. Specifically, 18% - 44% of the externalizing-internalizing co-occurred children and adolescents stayed in this subgroup over time. Most of the children and adolescents of co-occurrence subgroup came from the prior pure externalizing subgroup, and developed into pure internalizing group. Among all the psychopathology subgroups, the co-occurrence subgroup had the smallest likelihood to transit into the normal group. In terms of the co-development of externalizing and internalizing problems, researchers reported a subgroup consisted of 3.2% - 3.7% of children and adolescents that characterized by chronically high trajectories of both externalizing and internalizing problems. Developmental change of co-occurrence was also evident, as another typical co-development trajectories is characterized by decreases in both externalizing and internalizing problems through development. The co-occurrence of externalizing and internalizing problems is also distinct from the occurrence of a single problem. As demonstrated by prior studies, children with co-occurred externalizing and internalizing problems would have impaired social relationships with peers in adolescence. For the adolescents, they might suffer severe psychosocial problems later in late adolescence or adulthood, such as suicide, crime, and mental disorders. Turning to the reasons underlying externalizing-internalizing co-occurrence, previous studies revealed multiple individual and contextual factors that set it up. Specifically, boys are at higher risks of having the co-occurrence, though the development of co-occurrence did not show much gender difference. Studies have consistently shown that the temperament of negative emotionality is strongly related to externalizing-internalizing co-occurrence. Negative parenting practices and adverse peer relations, such as abuse, psychological control, school bullying, constitute important contextual risk factors of externalizing-internalizing co-occurrence. From the perspective of developmental cascade, researchers also deposited that the co-occurrence is resulted from a developmental process that one problem lead to another. Considering limitations of the literature, future studies regarding externalizing-internalizing co-occurrence can be advanced with two theoretical frameworks. The first is developmental cascade, by which the future researchers can systematically investigate the developmental path of genetic, neural, temperamental factors leading to externalizing-internalizing co-occurrence. The second is the interaction between multiple individual factors and contextual factors, which allows future studies to reveal the contributions of the factors of different levels and domains. The employment of the two frameworks would lead to more systematic and holistic understanding of co-occurrence of externalizing and internalizing problems among children and adolescence.

Key words: children and adolescence, psychopathology, externalizing and internalizing problems, co-occurrence, co-development

摘要： 儿童青少年内外化心理病理问题存在共发现象，已受到发展心理学和心理病理学研究者的广泛关注。本文对当前关于儿童青少年内外化问题的描述性研究和解释性研究进行了梳理，对儿童青少年共发现象发生率、发展特点、预测因素和发展结果等方面的重要研究发现进行系统性介绍。最后，基于发展级联和个体与环境因素交互作用视角，对未来本领域的研究进行展望，以期系统、完整地揭示内外化问题共发的原因。

关键词: 儿童青少年, 心理病理问题, 内外化问题, 共发, 共同发展