The purpose of this study was to provide a review of the publications of the risk perceptions or anxiety regarding radiation among people living in Japan after the 2011 Fukushima nuclear power plant accident. Two database (MEDLINE and PsycINFO) and hand-searched the references in identified publications were searched. For each identified publication, the measurements and time related-change of risk perception and anxiety regarding radiation were summarized. Twenty-four publications were identified. Quantitative measures of risk perception or anxiety were roughly divided into two types: single-item Likert scales that measure anxiety about radiation; and theoretical, or model-based measures. Rates of Fukushima residents with radiation-related anxiety decreased from 2012 to 2015. Factors governing risk perception or radiation-related anxiety were summarized by demographics, disaster-related stressors, trusted information, and radiation-related variables. The effects of risk perception or anxiety regarding radiation were summarized as severe distress, intention to leave employment or not to return home, or other dimensions. This review provides summary of current findings on risk perception or anxiety regarding radiation in Japan after the accident. Further researches are needed about detailed statistical analysis for time-related change and causality among variables.

The Patient Health Questionnaire-9 (PHQ-9) is commonly used to screen for depressive disorder and for monitoring depressive symptoms. However, there are mixed findings regarding its factor structure (i.e., whether it has a unidimensional, two-dimensional, or bi-factor structure). Furthermore, its measurement invariance between non-clinical and clinical populations and that between patients with major depressive disorder (MDD) and MDD with comorbid anxiety disorder (AD) is unknown. Japanese adults with MDD (n = 406), MDD with AD (n = 636), and no psychiatric disorders (non-clinical population; n = 1,163) answered this questionnaire on the Internet. Confirmatory factor analyses showed that the bi-factor model had a better fit than the unidimensional and two-dimensional factor models did. The results of a multi-group confirmatory factor analysis indicated scalar invariance between the non-clinical and only MDD groups, and that between the only MDD and MDD with AD groups. In conclusion, the bi-factor model with two specific factors was supported among the non-clinical, only MDD, and MDD with AD groups. The scalar measurement invariance model was supported between the groups, which indicated the total or sub-scale scores were comparable between groups.

The 7-item Generalized Anxiety Disorder Scale (GAD-7) is commonly used to monitor anxiety symptoms. However, its factor structure has been inconsistent among competing models: unidimensional, two-dimensional, or higher order models. Additionally, it is unknown whether the scale has measurement invariance between populations with and without self-reported psychiatric diagnostic status. Participants were Japanese adults with self-reported anxiety disorder (AD; n = 479), self-reported AD and major depressive disorder (MDD; n = 314), or without self-reported psychiatric diagnostic status (self-reported non-MDD/AD; n = 654), who completed this questionnaire on the Internet. Confirmatory factor analyses showed the higher order model had similar fit indices to the unidimensional and two-dimensional factor models. For the higher order model of GAD-7, metric invariance was supported between the self-reported non-MDD/AD and self-reported AD status groups, and scalar invariance was supported between the self-reported AD status and self-reported AD with MDD status groups. Moreover, convergent and discriminant validity were consistent with previous findings in Western cultures. These results suggest that factor loadings are equivalent and the construct has the same meaning between the self-reported non-MDD/AD and self-reported AD status groups, and the total or sub-scale scores were comparable between self-reported AD status and self-reported AD with MDD status groups. The major limitation of this study is that the participants’ diagnoses were self-reported, not confirmed by clinical structured interview. Further studies that incorporate clinical structured interviews are needed.

This paper discusses how positive emotions can help maintain and improve mental health during the COVID-19 outbreak, taking into account examples of social interaction and positive psychology research efforts in Japanese context.