The totality of evidence from twin studies of suicide strongly suggests genetic contributions to liability for suicidal behavior. To further research progress in this area, an extensive discussion of design limitations, shortcomings of the literature and further points is provided, including sources of bias, gaps in the literature, errors in previous reviews, age and sex effects and twin-singleton differences in suicide risk, and notes from a history-of-science view.

A scientometric analysis of modern research on the second-to-fourth digit ratio (2D:4D), a widely studied putative marker for prenatal androgen action, is presented. In early 2009, this literature totalled more than 300 publications and, since its initiation in 1998, has grown at a rate slightly faster than linear. Key findings included evidence of publication bias and citation bias, incomplete coverage and outdatedness of existing reviews, and a dearth of meta-analyses in this field. 2D:4D research clusters noticeably in terms of researchers, institutions, countries, and journals involved. Although 2D:4D is an anthropometric trait, most of the research has been conducted at psychology departments, not anthropology departments. However, 2D:4D research has not been predominantly published in core and specialized journals of psychology, but rather in more broadly scoped journals of the behavioral sciences, biomedical social sciences, and neurosciences. Total citation numbers of 2D:4D papers for the most part were not larger than their citation counts within 2D:4D research, indicating that until now, only a few 2D:4D studies have attained broader interest outside this specific field. Comparative citation analyses show that 2D:4D research presently is commensurate in size and importance to evolutionary psychological jealousy research, but has grown faster than the latter field. In contrast, it is much smaller and has spread more slowly than research about the Implicit Association Test Fifteen conjectures about anticipated trends in 2D:4D research are outlined, appendixed by a first-time bibliography of the entirety of the published 2D:4D literature.

Following the logic of the migrant study design of genetic epidemiology, the correspondence of IMM and COB suicide rates is consistent with the assumption of population differences in the prevalence of genetic risk factors for suicide.

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Convergent lines of evidence from adoption, family, geographical, immigrant, molecular genetic, surname, and twin studies of suicide point to genetic contributions to risk factors for suicidal behavior. Related mental health literacy (knowledge and beliefs) of professionals and laypersons may, however, lag behind this research progress. The purpose of this study was to further validate the 22-item Beliefs in the Inheritance of Risk Factors for Suicide Scale (BIRFSS), a novel instrument for assessing individuals' beliefs in the genetics of suicide. Data from a general population sample of 159 Austrian adults showed adequate internal scale consistency. Due to deliberate content heterogeneity, the instrument has a subscale structure, but factor analysis of items extracted a dominant first factor. BIRFSS scores were positively related to overall and specific knowledge on suicide facts (convergent validity), whereas unrelated to the Big Five personality dimensions, locus of control, social desirability, and verbal intelligence (discriminant validity). Demographic correlates of BIRFSS scores included respondents' age and religiosity (both positive ones), but not respondents' sex, educational level, or political orientation.