Mitochondria, often known as the cell’s powerhouses, are primarily responsible for generating energy through aerobic oxidative phosphorylation. However, their functions extend far beyond just energy production. Mitochondria play crucial roles in maintaining calcium balance, regulating apoptosis (programmed cell death), supporting cellular signaling, influencing cell metabolism, and synthesizing reactive oxygen species (ROS). Recent research has highlighted a strong link between bipolar disorder (BD) and mitochondrial dysfunction. Mitochondrial dysfunction contributes to oxidative stress, particularly through the generation of ROS, which are implicated in the pathophysiology of BD. Oxidative stress arises when there is an imbalance between the production of ROS and the cell’s ability to neutralize them. In neurons, excessive ROS can damage various cellular components, including proteins in neuronal membranes and intracellular enzymes. Such damage may interfere with neurotransmitter reuptake and the function of critical enzymes, potentially affecting brain regions involved in mood regulation and emotional control, which are key aspects of BD. In this review, we will explore how various types of mitochondrial dysfunction contribute to the production of ROS. These include disruptions in energy metabolism, impaired ROS management, and defects in mitochondrial quality control mechanisms such as mitophagy (the process by which damaged mitochondria are selectively degraded). We will also examine how abnormalities in calcium signaling, which is crucial for synaptic plasticity, can lead to mitochondrial dysfunction. Additionally, we will discuss the specific mitochondrial dysfunctions observed in BD, highlighting how these defects may contribute to the disorder’s pathophysiology. Finally, we will identify potential therapeutic targets to improve mitochondrial function, which could pave the way for new treatments to manage or mitigate symptoms of BD.

Understanding the tribological phenomena when fingers slide over soft surfaces such as skin is important for many practical applications. Therefore, this article analyzed the coefficients of friction for a bare finger sliding over artificial skin with different hardness under dry and lubricated surface conditions. This article contrasts with previous research that predominantly analyzed the contact between skin and hard surfaces or probes. Under dry conditions, the coefficient of friction was constant for artificial skins that were harder than the finger pad, irrespective of the normal force of the finger. However, the coefficient of friction decreased with increasing normal force for softer artificial skins. When the surface of the artificial skin model was lubricated with mica, the coefficient of friction exhibited normal-force dependence only for soft artificial skins, similar to the observations under dry conditions. This effect was due to the deformation friction; thus, the coefficient of friction increased as the normal force increased. Conversely, when the model was lubricated with ${\mathrm{ TiO}}_2$, the coefficient of friction depended on the normal force for all hardness levels. These findings provide insights into the friction experienced during skin-skin or skin-soft material contact under dry and lubricated conditions that can easily occur in daily life. Thus, the results of this study can be useful for the development of skin care products or assistive robots involving human-robot contact.

Aims: This study aimed to identify stress‐related factors associated with loneliness among Japanese university students and examine gender differences in these associations to apply gender‐specific mental health interventions.Methods: A total of 1642 university students (900 men, 742 women, mean age 20.0 ± 1.7 years) participated in an annual mental health survey conducted in 2024 for a university in Osaka Prefecture. Participants completed the Short‐Form UCLA Loneliness Scale, the Counseling Center Assessment of Psychological Symptoms, and the Perceived Stress Scale. Multiple linear regression analyses were performed separately for men and women, with loneliness as the dependent variable.Results: Depression and social anxiety were significant predictors of loneliness in both genders. Higher levels of loneliness were associated with living with others, lower alcohol consumption, and higher perceived stress in men, whereas family stress was associated with loneliness in women. Living alone, alcohol use, and perceived stress did not significantly predict loneliness in women.Conclusions: Depression and social anxiety are key factors associated with loneliness among university students, irrespective of their gender. Living alone, alcohol use, perceived stress, and family distress were gender‐specific factors associated with loneliness. Mental health interventions should consider gender‐specific needs, particularly addressing family‐related stress in women and enhancing socialization in men, to effectively reduce loneliness and its associated negative outcomes.

Background: The coronavirus disease 2019 (COVID-19) pandemic has profoundly impacted lives worldwide, influencing the incidence and severity of health problems. This may have affected the occurrence of workers’ sickness absences. This study aims to examine the incidence of long-term sickness absences due to mental disorders from 2009 to 2022 and the impact of the COVID-19 pandemic from the beginning of the COVID-19 pandemic (2020) to the end of the COVID-19 pandemic (2022). Methods: A retrospective observational design was employed. An anonymized record of public servants in City A with long-term sickness absences (≥ 90 days) from 2009 to 2022 was obtained. We defined 2009–2019 as the pre-COVID-19 pandemic period and 2020–2022 as the COVID-19 pandemic period. The influence of the COVID-19 pandemic on each disease category, classified using the ICD-10, was analyzed through interrupted time series analysis (ITSA) to evaluate changes in long-term sickness absences incidence before and during the COVID-19 pandemic period and the Cochran‒Armitage test to estimate trends in incidence rates over time. Results: Mental and behavioural disorders consistently demonstrated the highest incidence rates among all disease categories, with mood disorders being the most prevalent. Trends for all diseases analyzed did not change due to the COVID-19 pandemic. However, both ITSA and the Cochran‒Armitage test revealed increasing trends for depressive states and adjustment disorders throughout the study period. Conclusions: The COVID-19 pandemic did not influence the incidence of long-term sickness absences. However, depressive states and adjustment disorders exhibited an upward trend. This study underscores the need for tailored workplace mental health interventions to tackle the increasing stress-related illnesses, necessitating future research exploring the root causes.

Background: Over the years, occupations and workplaces have become more gender neutral as female participation in the workforce has risen. However, few studies have reported how the gender composition of the workplace affects occupational stress. Objective: This study aims to evaluate the relationship between gender composition and occupational stress among Japanese public servants. Methods: This cross-sectional study, conducted in 2019, included 18,486 public servants from City A, Japan, using data from the Brief Job Stress Questionnaire (BJSQ). After exclusions, 16,444 participants were analyzed based on their BJSQ scores. Workplaces were categorized according to their gender compositions: female- or male-dominated, and gender-neutral. Multivariable logistic regression was used to estimate the odds ratios (OR) for the effect of gender composition on mental health, after adjusting for demographic and occupational factors. Results: Among females, high job stressors were associated with both female- and male-dominated workplaces, and high stress responses were associated with male-dominated workplaces. Among males, high job stressors and high stress responses were associated with both female- and male-dominated workplaces. Conclusions: Female-dominated workplaces were associated with high occupational stress. In contrast, male-dominated workplaces were associated with low occupational stress. Understanding the differences in occupational stress due to gender composition may play an important role in creating a more equitable and effective work environment.