Association of 7 million+ tweets featuring suicide-related content with daily calls to the Suicide Prevention Lifeline and with suicides, United States, 2016-2018.

OBJECTIVE: The aim of this study was to assess associations of various content areas of Twitter posts with help-seeking from the US National Suicide Prevention Lifeline (Lifeline) and with suicides. METHODS: We retrieved 7,150,610 suicide-related tweets geolocated to the United States and posted between 1 January 2016 and 31 December 2018. Using a specially devised machine-learning approach, we categorized posts into content about prevention, suicide awareness, personal suicidal ideation without coping, personal coping and recovery, suicide cases and other. We then applied seasonal autoregressive integrated moving average analyses to assess associations of tweet categories with daily calls to the US National Suicide Prevention Lifeline (Lifeline) and suicides on the same day. We hypothesized that coping-related and prevention-related tweets are associated with greater help-seeking and potentially fewer suicides. RESULTS: The percentage of posts per category was 15.4% (standard deviation: 7.6%) for awareness, 13.8% (standard deviation: 9.4%) for prevention, 12.3% (standard deviation: 9.1%) for suicide cases, 2.4% (standard deviation: 2.1%) for suicidal ideation without coping and 0.8% (standard deviation: 1.7%) for coping posts. Tweets about prevention were positively associated with Lifeline calls (B = 1.94, SE = 0.73, p = 0.008) and negatively associated with suicides (B = -0.11, standard error = 0.05, p = 0.038). Total number of tweets were negatively associated with calls (B = -0.01, standard error = 0.0003, p = 0.007) and positively associated with suicide, (B = 6.4 × 10-5, standard error = 2.6 × 10-5, p = 0.015). CONCLUSION: This is the first large-scale study to suggest that daily volume of specific suicide-prevention-related social media content on Twitter corresponds to higher daily levels of help-seeking behaviour and lower daily number of suicide deaths. PREREGISTRATION: As Predicted, #66922, 26 May 2021.

Mindfulness-Based Mobile Apps and Their Impact on Well-Being in Nonclinical Populations: Systematic Review of Randomized Controlled Trials.

BACKGROUND: Mindfulness-based mobile apps have become popular tools for enhancing well-being in today's fast-paced world. Their ability to reduce geographical, financial, and social barriers makes them a promising alternative to traditional interventions. OBJECTIVE: As most available apps lack a theoretical framework, this review aimed to evaluate their effectiveness and assess their quality. We expected to find small sample sizes, high dropout rates, and small effect sizes in the included studies. METHODS: A systematic literature search was conducted using PsycInfo, PsycNet, PubMed, an institutional search engine (u:search), and Google Scholar. Randomized controlled trials assessing the impact of mobile mindfulness apps on well-being in nonclinical samples were included. Study selection, risk of bias (using the version 2 of the Cochrane risk-of-bias tool for randomized trials), and reporting quality (using selected CONSORT [Consolidated Standards of Reporting Trials] statement criteria) assessments were performed by 2 authors independently and discussed until a consensus was reached. RESULTS: The 28 included randomized controlled trials differed in well-being measures, apps, and intervention duration (7 to 56 days; median duration 28 days). A wide range of sample sizes (12 to 2282; median 161) and attrition rates (0% to 84.7%; median rate 23.4%) were observed. Most studies (19/28, 68%) reported positive effects on at least one aspect of well-being. The effects were presented using different metrics but were primarily small or small to medium in size. Overall risk of bias was mostly high. CONCLUSIONS: The wide range of sample sizes, attrition rates, and intervention periods and the variation in well-being measures and mobile apps contributed to the limited comparability of the studies. Although most studies (16/28, 57%) reported small or small to medium effects for at least one well-being outcome, this review demonstrates that the generalizability of the results is limited. Further research is needed to obtain more consistent conclusions regarding the impact of mindfulness-based mobile apps on well-being in nonclinical populations.

Only Small Effects of Mindfulness-Based Interventions on Biomarker Levels of Inflammation and Stress: A Preregistered Systematic Review and Two Three-Level Meta-Analyses.

Mindfulness-based interventions (MBIs) have a positive effect on biomarkers of inflammation and stress in patients with psychiatric disorders and physical illnesses. Regarding subclinical populations, results are less clear. The present meta-analysis addressed the effects of MBIs on biomarkers in psychiatric populations and among healthy, stressed, and at-risk populations. All available biomarker data were investigated with a comprehensive approach, using two three-level meta-analyses. Pre-post changes in biomarker levels within treatment groups (k = 40 studies, total N = 1441) and treatment effects compared to control group effects, using only RCT data (k = 32, total N = 2880), were of similar magnitude, Hedges g = -0.15 (95% CI = [-0.23, -0.06], p < 0.001) and g = -0.11 (95% CI = [-0.23, 0.001], p = 0.053). Effects increased in magnitude when including available follow-up data but did not differ between type of sample, MBI, biomarker, and control group or duration of the MBI. This suggests that MBIs may ameliorate biomarker levels in both psychiatric and subclinical populations to a small extent. However, low study quality and evidence of publication bias may have impacted on the results. More large and preregistered studies are still needed in this field of research.

Suicide mortality in the United States following the suicides of Kate Spade and Anthony Bourdain.

OBJECTIVE: The suicides of Kate Spade and Anthony Bourdain, two major American icons, in a span of days in June 2018 represent a unique and tragic natural experiment to characterize associations with actual suicides in the aftermath of celebrity suicides. The aim of this study was to identify changes in suicide counts after their deaths. METHODS: Suicide data were obtained from the United States' Centers for Disease Control and Prevention's public-use mortality file. A time-series analysis was performed, examining monthly suicide data by age group (⩽19, 20-44, 45-64 and ⩾65 years), for both men and women, for all suicide methods and for hanging versus non-hanging methods, from January 1999 to December 2018. Seasonal autoregressive integrated moving-average models were fitted to the pre-June 2018 period, estimating suicides in subsequent months and identifying deviations from expected values. The volume of Twitter posts about Kate Spade and Anthony Bourdain was used as a proxy of societal attention. RESULTS: Tweets about the celebrities were mainly concentrated in June 2018 and faded quickly in July. Total suicides exceeded the 95% confidence interval for June and approximated the upper limit of the 95% confidence interval in July. Over this 2-month span, there were 418 (95% confidence interval = [184, 652]) more suicides than expected, including 275 (95% confidence interval = [79, 471]) excess suicides in men and 182 (95% confidence interval = [93, 271]) in women. These equate to 4.8%, 4.1% and 9.1% increases above expected counts. There were 392 (95% confidence interval = [271, 514]) excess suicides by hanging, a 14.5% increase, with no significant increase in all other methods combined. CONCLUSION AND RELEVANCE: These findings demonstrate that mortality following celebrity suicides can occur at a similar magnitude to that observed for other public health emergencies. They underscore the urgency for interventions to mitigate imitation effects after celebrity suicide reporting.

The Impact of Educative News Articles about Suicide Prevention: A Randomized Controlled Trial.

Media stories featuring stories of personal experiences of coping with suicidal ideation have been shown to decrease suicide risk, but it is unclear whether more impersonal awareness materials have similar effects. This study aimed to test the impact of impersonal educative news articles featuring interviews with suicide prevention experts. Because the impact of news articles may be determined by the articles' pull quotes and headlines, we also aimed to compare the impact of two versions of the same suicide prevention news article. One version featured headlines and pull quotes highlighting the message that suicide is preventable, whereas the other version focused on the message that suicide is prevalent. In a web-based randomized controlled trial, n = 425 participants either read a news article featuring a prevention expert with one of the above versions of the same text or an article unrelated to suicide. Data on suicidal ideation, stigmatizing attitudes toward suicidal individuals, policy attitudes toward suicide prevention, help-seeking intentions, and assumptions on the prevalence of suicide-related behavior were measured with questionnaires. The assumed prevalence of suicide in the population was greater in both intervention groups than in the control group, but the articles did not have an impact on other outcomes, and there were no differences for variations in headlines and pull quotes. Impersonal suicide prevention articles appear safe to use and do not have an impact on suicide risk factors in general population samples.

Charting the landscape of graphical displays for meta-analysis and systematic reviews: a comprehensive review, taxonomy, and feature analysis.

BACKGROUND: Data-visualization methods are essential to explore and communicate meta-analytic data and results. With a large number of novel graphs proposed quite recently, a comprehensive, up-to-date overview of available graphing options for meta-analysis is unavailable. METHODS: We applied a multi-tiered search strategy to find the meta-analytic graphs proposed and introduced so far. We checked more than 150 retrievable textbooks on research synthesis methodology cover to cover, six different software programs regularly used for meta-analysis, and the entire content of two leading journals on research synthesis. In addition, we conducted Google Scholar and Google image searches and cited-reference searches of prior reviews of the topic. Retrieved graphs were categorized into a taxonomy encompassing 11 main classes, evaluated according to 24 graph-functionality features, and individually presented and described with explanatory vignettes. RESULTS: We ascertained more than 200 different graphs and graph variants used to visualize meta-analytic data. One half of these have accrued within the past 10 years alone. The most prevalent classes were graphs for network meta-analysis (45 displays), graphs showing combined effect(s) only (26), funnel plot-like displays (24), displays showing more than one outcome per study (19), robustness, outlier and influence diagnostics (15), study selection and p-value based displays (15), and forest plot-like displays (14). The majority of graphs (130, 62.5%) possessed a unique combination of graph features. CONCLUSIONS: The rich and diverse set of available meta-analytic graphs offers a variety of options to display many different aspects of meta-analyses. This comprehensive overview of available graphs allows researchers to make better-informed decisions on which graphs suit their needs and therefore facilitates using the meta-analytic tool kit of graphs to its full potential. It also constitutes a roadmap for a goal-driven development of further graphical displays for research synthesis.

Associations of Bisexuality and Homosexuality with Handedness and Footedness: A Latent Variable Analysis Approach.

Non-right-handedness appears to be more common among bisexuals and homosexuals than among heterosexuals, which might be indirect evidence of effects of prenatal androgen exposure. Current data suggest higher prenatal testosterone levels among bisexual and homosexual women, but are inconclusive for men. This study examined the association between sexual orientation and non-right-handedness for sex differences and whether higher rates of mixed-handedness, rather than left-handedness, might be the driving factor. This allowed for more specific tests regarding the predictions of two competing theories of prenatal androgen exposure, the Geschwind-Galaburda theory and the callosal hypothesis, than in previous research. Being a potentially better indicator of cerebral lateralization than handedness, associations with footedness were also explored. To counter inconsistencies and shortcomings of previous research, we utilized two large discovery and replication datasets (ns = 2368 and 1565) and applied latent variable analysis to reliably classify lateral preferences (i.e., handedness, footedness). This maximized the statistical conclusion validity and allowed for direct tests of replicability. Sexual orientation was differentially associated with lateral preferences among men and women. Associations among women were consistent with predictions of the Geschwind-Galaburda theory, whereas among men they were consistent with predictions of the callosal hypothesis. The results were further consistent with models of homosexuality that suggest a role of parental epigenetic marks on sexually dimorphic fetal development. Research efforts should be increased with regard to footedness and epigenetic theories of homosexuality.

Suicides in Young People in Ontario Following the Release of "13 Reasons Why".

OBJECTIVE: "13 Reasons Why," a Netflix series, included a controversial depiction of suicide that has raised fears about possible contagion. Studies of youth suicide in the United States found an increase on the order of 10% following release of the show, but this has not been replicated in other countries. This study aims to begin to address that gap by examining the relationship between the show's release and youth suicide in Canada's most populous province. METHODS: Suicides in young people (under the age of 30) in the province of Ontario following the show's release on March 31, 2017, were the outcome of interest. Time-series analyses were performed using data from January 2013 to March 2017 to predict expected deaths from April to December 2017 with a simple seasonal model (stationary R 2 = 0.732, Ljung-Box Q = 15.1, df = 16, P = 0.52, Bayesian information criterion = 3.09) providing the best fit/used for the primary analysis. RESULTS: Modeling predicted 224 suicides; however, 264 were observed corresponding to 40 more deaths or an 18% increase. In the primary analysis, monthly suicides exceeded the 95% confidence limit for 3 of the 9 months (May, July, and October). CONCLUSION: The statistical strength of the findings here is limited by small numbers; however, the results are in line with what has been observed in the United States and what would be expected if contagion were occurring. Further research in other locations is needed to increase confidence that the associations found here are causal.

META-ANALYSIS SHOWS ASSOCIATIONS OF DIGIT RATIO (2D:4D) AND TRANSGENDER IDENTITY ARE SMALL AT BEST.

ABBREVIATIONS: 2D:4D = digit ratio; CI = confidence interval; F = female; FtM = female-to-male transgender; M = male; MtF = male-to-female transgender; TGI = transgender identity.

"A joke a day keeps the doctor away?" Meta-analytical evidence of differential associations of habitual humor styles with mental health.

Humor and mental health are interconnected as is evidenced by a large number of studies. However, associations are only small and inconsistent as the operationalization of humor poses a methodological challenge. The Humor Styles Questionnaire (HSQ) differentiates four humor styles that might be beneficial or harmful to mental health. The aim of the present study was to meta-analytically aggregate studies using the HSQ to assess the associations of different humor styles with four areas of mental health (self-esteem, life satisfaction, optimism, depression). An extensive electronic database literature search identified 37 studies that reported correlations between the HSQ scales and the four areas of mental health in 45 independent samples (total N = 12,734). In total, 16 meta-analyses were conducted. Moderating effects of participant age, sex, and geographic region were examined via subgroup analyses and meta-regression. Humor styles differed in terms of their associations with mental health. Health-promoting humor styles were overall positively correlated with mental health (small-to-medium effect sizes). Self-defeating humor was overall negatively correlated with mental health. Aggressive humor was overall unrelated with mental health. Moderator analyses suggested geographic differences (Eastern vs. Western samples) and sex differences for some of these associations. Fostering specific humor styles may be beneficial for mental health. In addition, observing the habitual use of humor styles might help therapists to develop a better understanding of their clients. Differences in the utilization and the correlates of humor styles in Eastern and Western societies, and sex differences, need to be addressed in future research.

Monitoring unfractionated heparin in children: a parallel-cohort randomized controlled trial comparing 2 dose protocols.

Monitoring unfractionated heparin (UFH) is crucial to prevent over- or under-anticoagulation. However, the optimal parameters for monitoring UFH in children are not well established. The study objectives were to investigate (1) the relationship between UFH dose and its anticoagulant effect as assessed by anti-Xa, activated partial thromboplastin time (aPTT) and activated clotting time (ACT); (2) other factors influencing UFH effect; (3) the agreement between the assays; and (4) the association between UFH effect and clinical outcome. HEARTCAT was a parallel-cohort randomized controlled trial comparing high-dose (100 U/kg bolus followed by age-based continuous infusion in randomized children) vs low-dose UFH (50 U/kg bolus) during cardiac catheterization in children. Blood samples were drawn before and after UFH administration at 30, 60, and 90 minutes. Four-hundred and two samples of 149 patients were evaluable. Anti-Xa, aPTT, and ACT all showed good discrimination between UFH doses. Regression models demonstrated the following determinants of UFH effect: UFH dose, age, baseline antithrombin (for anti-Xa), and baseline levels of aPTT and ACT, respectively. UFH effects were lower in infants compared with older children, which was more pronounced at low-dose than at high-dose UFH. Agreement between the 3 assays was poor. Most aPTT values were above therapeutic range or beyond measuring limit and thus of limited value for UFH monitoring. No association of UFH dose or effect with clinical outcome could be observed. In conclusion, all assays reflected a significant UFH dose-effect relationship, however, with poor agreement between the respective tests. The age-dependency of UFH effect was confirmed. Notably, the influence of age on UFH effect was dose-dependent.

Beneficial and harmful effects of educative suicide prevention websites: randomised controlled trial exploring Papageno v. Werther effects.

BackgroundSuicide prevention organisations frequently use websites to educate the public, but evaluations of these websites are lacking.AimsTo examine the effects of educative websites and the moderating effect of participant vulnerability.MethodA total of 161 adults were randomised to either view an educative website on suicide prevention or an unrelated website in a single-blinded randomised controlled trial (trial registration with the American Economic Association's registry: RCT-ID: 000924). The primary outcome was suicidal ideation; secondary outcomes were mood, suicide-prevention-related knowledge and attitudes towards suicide/seeking professional help. Data were collected using questionnaires before (T1), immediately after exposure (T2), and 1 week after exposure (T3) and analysed using linear mixed models.ResultsNo significant intervention effect was identified for the entire intervention group with regard to suicidal ideation, but a significant and sustained increase in suicide-prevention-related knowledge (T3vT1P < 0.001, d = 1.12, 95% CI 0.96 to 1.28) and a non-sustained worsening of mood (P < 0.001, T2vT1, d = -0.59, -0.75 to -0.43) were observed. Participants with increased vulnerability experienced a partially sustained reduction of suicidal ideation (T3vT1, P <0.001, d = -0.34, -0.50 to -0.19).ConclusionsEducative professional suicide prevention websites appeared to increase suicide-prevention-related knowledge, and among vulnerable individuals website exposure may be associated with a reduction of suicidal ideation.

Genetic and Environmental Sources of Implicit and Explicit Self-Esteem and Affect: Results from a Genetically Sensitive Multi-group Design.

In today's world, researchers frequently utilize indirect measures of implicit (i.e., automatic, spontaneous) evaluations. The results of several studies have supported the usefulness of these measures in predicting behavior, as compared to utilizing direct measures of explicit (i.e., purposeful, deliberate) evaluations. A current, under-debate issue concerns the origin of these implicit evaluations. The present genetically sensitive multi-group study analyzed data from 223 twin pairs and 222 biological core families to estimate possible genetic and environmental sources of individual differences in implicit and explicit self-esteem and affect. The results show that implicit self-esteem and affect maintain a substantial genetic basis, but demonstrate little influence from the shared environment by siblings (e.g., shared familial socialization in childhood). A bivariate analysis found that implicit and explicit evaluations of the same construct share a common genetic core which aligns with the motivation and opportunity as determinants (MODE) model.

Unto the third generation: evidence for strong familial aggregation of physicians, psychologists, and psychotherapists among first-year medical and psychology students in a nationwide Austrian cohort census.

BACKGROUND: Medical students present higher numbers of physician relatives than expectable from the total population prevalence of physicians. Evidence for such a familial aggregation effect of physicians has emerged in investigations from the Anglo-American, Scandinavian, and German-speaking areas. In particular, past data from Austria suggest a familial aggregation of the medical, as well as of the psychological and psychotherapeutic, professions among medical and psychology undergraduates alike. Here, we extend prior related studies by examining (1) the extent to which familial aggregation effects apply to the whole nation-wide student census of all relevant (eight) public universities in Austria; (2) whether effects are comparable for medical and psychology students; (3) and whether these effects generalize to relatives of three interrelated health professions (medicine, psychology, and psychotherapy). METHODS: We investigated the familial aggregation of physicians, psychologists, and psychotherapists, based on an entire cohort census of first-year medical and psychology students (n = 881 and 920) in Austria with generalized linear mixed models. RESULTS: For both disciplines, we found strong familial aggregation of physicians, psychologists, and psychotherapists. As compared with previous results, directionally opposite time trends within disciplines emerged: familial aggregation of physicians among medical students has decreased, whilst familial aggregation of psychologists among psychology students has increased. Further, there were sex-of-relative effects (i.e., more male than female physician relatives), but no substantial sex-of-student effects (i.e., male and female students overall reported similar numbers of relatives for all three professions of interest). In addition, there were age-benefit effects, i.e., students with a relative in the medical or the psychotherapeutic profession were younger than students without, thus suggesting earlier career decisions. CONCLUSIONS: The familial aggregation of physicians, psychologists, and psychotherapists is high among medical and psychology undergraduates in Austria. Discussed are implications of these findings (e.g., gender equity, feminization of the medical field, ideas for curricular implementation and student counselling), study limitations, and avenues for future research.

The relative efficacy of bona fide psychotherapies for post-traumatic stress disorder: a meta-analytical evaluation of randomized controlled trials.

BACKGROUND: In the treatment of PTSD, meta-analyses suggest comparable efficacy of cognitive behavioural therapies and various trauma focused treatments, but results for other treatments are inconsistent. One meta-analysis found no differences for bona fide therapies, but was critizised for overgeneralization and a biased study sample and relied on an omnibus test of overall effect size heterogeneity that is not widely used. METHODS: We present an updated meta-analysis on bona fide psychotherapies for PTSD, contrasting an improved application of the omnibus test of overall effect size heterogeneity with conventional random-effects meta-analyses of specified treatment types against all others. Twenty-two studies were eligible, reporting 24 head-to-head comparisons in randomized controlled trials of 1694 patients. RESULTS: Head-to-head comparison between trauma focused and non-trauma focused treatments revealed a small relative advantage for trauma focused treatments at post-treatment (Hedges' g = 0.14) and at two follow-ups (g = 0.17, g = 0.23) regarding PTSD symptom severity. Controlling and adjusting for influential studies and publication bias, prolonged exposure and exposure therapies (g = 0.19) were slightly more efficacious than other therapies regarding PTSD symptom severity at post-treatment; prolonged exposure had also higher recovery rates (RR = 1.26). Present-centered therapies were slightly less efficacious regarding symptom severity at post-treatment (g = -0.20) and at follow-up (g = -0.17), but equally efficacious as available comparison treatments with regards to secondary outcomes. The improved omnibus test confirmed overall effect size heterogeneity. CONCLUSIONS: Trauma focused treatments, prolonged exposure and exposure therapies were slightly more efficacious than other therapies in the treatment of PTSD. However, treatment differences were at most small and far below proposed thresholds of clinically meaningful differences. Previous null findings may have stemmed from not clearly differentiating primary and secondary outcomes, but also from a specific use of the omnibus test of overall effect size heterogeneity that appears to be prone to error. However, more high-quality studies using ITT analyses are still needed to draw firm conclusions. Moreover, the PTSD treatment field may need to move beyond a focus primarily on efficacy so as to address other important issues such as public health issues and the requirements of highly vulnerable populations.

The influence of sense of coherence and mindfulness on PTSD symptoms and posttraumatic cognitions in a sample of elderly Austrian survivors of World War II.

BACKGROUND: Sense of Coherence (SOC) and mindfulness are known protective factors against psychopathology, also in older age. We set out to investigate the influence of SOC and mindfulness on posttraumatic symptoms and cognitions in the context of lifetime trauma in elderly persons with a history of childhood war-experiences. METHODS: Elderly Austrians (N = 97) filled in questionnaires on traumatic lifetime experiences and posttraumatic symptoms (ETI), posttraumatic cognitions (PTCI), SOC (SOC-13) and mindfulness (FFMQ). We expected the influence of SOC scores on posttraumatic symptoms and cognitions to be on one hand influenced by mindfulness. On the other hand, we expected that both aspects would uniquely explain fewer posttraumatic symptoms and cognitions. RESULTS: Participants reported various lifetime traumas (M = 2.42), including experiences during World War II (WWII) as children and adolescents. Mindfulness partially mediated the association of SOC scores with posttraumatic cognitions, but not with posttraumatic symptoms. However, in a two-stage mediation model, mindfulness significantly predicted posttraumatic symptoms via its effects on posttraumatic cognitions. CONCLUSION: Although SOC was the strongest predictor of posttraumatic symptoms, mindfulness influenced the severity of posttraumatic symptoms via its effects on posttraumatic cognitions. We discuss implications for mindfulness-based interventions on trauma-related cognitions in the elderly.

Cross-national comparisons of attitudes towards suicide and suicidal persons in university students from 12 countries.

This paper reports the results of a comparative investigation of attitudes to suicide and suicidal persons in 5,572 university students from 12 countries. Participants filled out two scales measuring attitudes towards suicide and suicidal persons, a measure of psychological distress together with the questions about suicidal behavior. Results showed that the highest suicide acceptance scores were observed in Austrian, UK, Japanese and Saudi Arabian samples and the lowest scores were noted in Tunisian, Turkish, Iranian and Palestinian samples. While the highest social acceptance scores for a suicidal friend were noted in Turkish, US, Italian and Tunisian samples, the lowest scores were seen in Japanese, Saudi Arabian, Palestinian and Jordanian samples. Compared to participants with a suicidal past, those who were never suicidal displayed more internal barriers against suicidal behavior. Men were more accepting of suicide than women but women were more willing to help an imagined suicidal peer. Participants with accepting attitudes towards suicide but rejecting attitudes towards suicidal persons reported more suicidal behavior and psychological distress, and were more often from high suicide rate countries and samples than their counterparts. They are considered to be caught in a fatal trap in which most predominant feelings of suicidality such as hopelessness or helplessness are likely to occur. We conclude that in some societies such as Japan and Saudi Arabia it might be difficult for suicidal individuals to activate and make use of social support systems.

Evidence of Sex-Linked Familial Transmission of Lateral Preferences for Hand, Foot, Eye, Ear, and Overall Sidedness in a Latent Variable Analysis.

This study investigated the familial transmission of handedness, footedness, eyedness, earedness, and of underlying sidedness in a sample of adults (n = 592 families; 1528 individuals in total), using multi-item inventories and probabilistic methods for preference classification. Our results corroborate three classes of lateral preferences and of sidedness each, right, mixed, and left. Consistent with genetic studies, we obtained evidence of parent-of-origin and sex-of-children effects, suggesting important roles of maternal mixed preferences and of paternal left preferences. Further, parental age at conception predicted mixed preferences in the child. We recommend a trichotomous classification of lateral preferences also in future studies, and to intensify research into the genetic bases of footedness, eyedness and earedness.