Negative Life Events and Problematic Internet Use as Factors Associated With Psychotic-Like Experiences in Adolescents

Objectives: Psychotic-like experiences (PLEs) and problematic internet use (PIU) are common in adolescents. However, little is known about the association between PLEs and PIU among adolescents. The present study examined the associations between PLEs and PIU and negative life events among adolescents.Methods: In total, 1,678 adolescents attending high school were recruited for a cross-sectional survey. They completed self-reported assessments of PLEs using the Prodromal Questionnaire-16 (PQ-16) and measures of depression, anxiety, self-esteem, internet use, and negative life events using the Center for Epidemiological Studies Depression Scale (CES-D), the State-Trait Anxiety Inventory (STAI), the Rosenberg Self-Esteem Scale (RSES), the Korean Scale for Internet Addiction (K-scale), and the Lifetime Incidence of Traumatic Events for Children (LITE-C), including cybersexual harassment and school violence.Results: A total of 1,239 subjects (73.8%) scored at least 1 on the PQ-16. The mean total and distress PQ-16 scores were significantly higher in students who used mental health services. The total and distress prodromal questionnaire-16 (PQ-16) scores were positively correlated with the CES-D, STAI-S, STAI-T, LITE-C, and K-scale scores but negatively correlated with the RSES score. Hierarchical linear regression analysis revealed that PLEs were significantly associated with a high K-scale score and the incidence of negative life events, such as LITE-C, cybersexual harassment, and bully–victims.Conclusion: Our results demonstrate that PIU and negative life experiences were significantly associated with PLEs in adolescents. Assessment and therapeutic intervention with regard to internet use as a coping strategy for stress are needed to prevent the development of clinical psychotic symptoms

Interaction between the mouse homologue of CD99 and its ligand PILR as a mechanism of T cell receptor-independent thymocyte apoptosis

Here, we show that the interaction between two membrane proteins, the mouse homologue of CD99 (designated D4) and its ligand, paired immunoglobulin-like type 2 receptor (PILR), is one of the major mechanisms of thymocyte apoptosis. Using the polymeric fusion protein of PILR and IgG1 (PILR-Ig), we demonstrated that D4 ligation in the absence of T cell receptor (TCR) engagement leads to the induction of apoptosis, mainly at the double-positive stage of thymocytes. This was further confirmed by a blocking study in which blocking the interaction between D4 and PILR by soluble D4 protein led to reduced apoptosis in the fetal thymic organ culture with wild type and TCRα-/- mice. Furthermore, the dissection of intracellular signaling pathway demonstrated that D4 cross-linking led to caspase activation without any change in mitochondrial membrane potential. Based on these data, we propose a mechanism for thymocyte depletion in which the interaction between D4 and PILR delivers an active signal