Social isolation is associated with suicidal ideation (SI) and self-harm (SH) among adolescents. However, the association between preference for solitude (PfS), SI, and SH is unknown. The prevalence of adolescents who have both of PfS and social isolation and the risks for SI and SH among them are also unknown. Information on PfS, social isolation, SI, and SH was collected in a large-scale school-based survey on adolescents, using a self-report questionnaire. Associations between PfS, SI, and SH were examined by logistic regression analysis. The interactions between PfS and social isolation on SI and SH were also investigated. The odds of SI and SH were examined for groups defined by presence of PfS and social isolation. Responses from 17,437 students (89.3% of relevant classes) were available. After adjusting for demographic characteristics and social isolation, PfS was associated with increased odds of SI (odds ratio [OR] = 3.1) and SH (OR = 1.9). There was no interaction between PfS and social isolation on SI and SH. After adjusting for demographic characteristics, the odds for SI (OR = 8.6) and SH (OR = 3.8) were highest among adolescents with both PfS and social isolation (8.4% of all respondents). PfS was associated with increased odds of SI and SH in adolescents. No interaction effect between PfS and social isolation on SI and SH was found, but adolescents with PfS and social isolation had the highest risk for SI and SH. Parents and professionals should pay attention to suicide risk in adolescents with PfS.

Background: A child’s death is one of the most stressful events that parents and siblings may experience. Interventions for bereaved families following a child’s death have been examined over the last several decades. However, there is little high-quality evidence to support any rationale for determining optimal interventions for bereaved parents and siblings. Aim: This study objectives were to evaluate the efficacy of interventions for bereaved parents and siblings following a child’s death, to collect empirical evidence of the quality of these intervention studies, and to identify methodological challenges. Design: A systematic review of data from randomized controlled trials of interventions for parents or siblings bereaved after a child loss. Data sources: We searched MEDLINE (from 1949), PsycINFO (from 1806), and CINAHL (from 1806) databases for key terms and checked the reference lists of potentially relevant articles. Results: We identified nine articles describing eight eligible trials from which we extracted data. The four types of intervention included support groups, counseling, psychotherapy, and crisis intervention. Most intervention trials showed some effect on participants in at least one outcome measure. However, we identified many severe methodological issues and outcome sets in these trials. Conclusion: Very little evidence of sufficient quality is available to confirm the effects of intervention measures on bereaved parents and siblings following a child’s death. Well-designed randomized controlled trials are needed to improve our understanding of the efficacy and implementation of interventions targeting bereaved parents and siblings.

A potential association between pet ownership and mental well-being is suggested, but there is a shortage of high-quality longitudinal studies that consider probable differences among different species. We aimed to examine whether ownership of the most popular pets (dogs and cats) would predict mental well-being. The Tokyo Teen Cohort (TTC), a prospective population-based birth cohort study, had dog and cat ownership data at age 10 and mental well-being score at ages 10 and 12 from 2584 adolescents. Linear regression analysis with adjusting for covariates showed that dog ownership had a positive effect on mental well-being compared to no dog ownership, however, cat ownership had a negative effect compared to no cat ownership. Two-factor mixed-design analysis of variance showed that dog ownership predicted maintained mental well-being, while cat ownership predicted progressing decline of mental well-being. Thus, dog and cat ownership may have different effects on adolescents’ mental well-being, implying that the underlying mechanisms that are activated by these types of ownership may differ.

Subcortical structures may have an important role in the pathophysiology of psychosis. Our recent mega-analysis of structural magnetic resonance imaging (MRI) data has reported subcortical volumetric and lateralization alterations in chronic schizophrenia, including leftward asymmetric increases in pallidal volume. The question remains, however, whether these characteristics may represent vulnerability to the development of psychosis or whether they are epiphenomena caused by exposure to medication or illness chronicity. Subclinical psychotic experiences (SPEs) occur in some adolescents in the general population and increase the odds of developing psychosis in young adulthood. Investigations into the association between SPEs and MRI-measured volumes of subcortical structures in the general adolescent population would clarify the issue. Here, we collected structural MRI data in a subsample (10.5–13.3 years old) of a large-scale population-based cohort and explored subcortical volume and lateralization alterations related to SPEs (N = 203). Adolescents with SPEs demonstrated significant volumetric increases in the left hippocampus, right caudate, and right lateral ventricle, as well as a marginally significant increase in the left pallidum. Furthermore, adolescents with SPEs showed significantly more leftward laterality of pallidal volume than individuals without SPEs, which replicates our mega-analysis findings in chronic schizophrenia. We suggest that leftward asymmetries in pallidal volume already present in early adolescence may underlie the premorbid predisposition for developing psychosis in later life.

Background: Adolescent loneliness is a growing public health issue owing to its adverse health impact. Although adolescent loneliness is common, its trajectories can show distinct patterns over time. However, there is limited knowledge regarding their determinants, particularly for chronic loneliness. We aimed to determine the predictors of loneliness trajectories across early-to-mid adolescence and examine their association with later suicidality. Methods: Data were collected from 3165 participants from the population-based Tokyo Teen Cohort. Participants reported their loneliness at 10, 12, 14, and 16 years. Loneliness trajectories were identified using latent class growth analysis. We examined the predictive role of bullying victimization and parental psychological distress at age 10 via a multinomial logistic regression. Sociodemographic and child-related factors (i.e., chronic health conditions and cognitive delay) were included as covariates. The association between the trajectories, self-harm, and suicidal ideation by age 16 was investigated using Poisson regression. Results: Four trajectories were identified: “consistently low” (2448, 77.3%), “moderate–decreasing” (185, 5.8%), “moderate–increasing” (508, 16.1%), and “consistently high” (24, 0.8%). Taking “consistently low” as a reference, experiences of bullying victimization predicted all the remaining trajectories [adjusted relative risk ratio 1.64, 95% confidence interval (CI) 1.18–2.28 for “moderate–decreasing,” 1.88, 1.52–2.33 for “moderate–increasing,” and 4.57, 1.97–10.59 for “consistently high”]. Parental psychological distress predicted the “moderate–increasing” (1.84, 1.25–2.71) and “consistently high” (5.07, 1.78–14.42) trajectories. The “consistently high” trajectory showed the greatest risk for self-harm and suicidal ideation (adjusted relative risk ratio 6.01, 95% CI 4.40–8.22; 2.48, 1.82–3.37, respectively); however, the “moderate–increasing” and “moderate–decreasing” trajectories were also at increased risk (moderate–increasing: 2.71, 2.23–3.30 for self-harm, 1.93, 1.69–2.19 for suicidal ideation; moderate–decreasing: 2.49, 1.91–3.26 for self-harm, 1.59, 1.33–1.91 for suicidal ideation). Conclusions: Bullying victimization and parental psychological distress at age 10 were independent determinants of increased and chronic loneliness trajectories across early-to-mid adolescence. Compared with “consistently low,” all other loneliness trajectories were associated with an increased risk of adolescent suicidality. Interventions targeting adolescent loneliness should include approaches to mitigate bullying and parental psychological distress. These strategies may help prevent adolescent suicidality.