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Background: Attention-deficit/hyperactivity disorder (ADHD) and body mass index (BMI) are associated. However, it remains unclear whether this association reflects causal relationships in either direction or confounding. Here, we implemented genetically informed methods to examine bidirectional causality and potential confounding.Methods: Three genetically informed methods were employed: (i) cross-lagged twin-differences analyses to assess bidirectional effects of ADHD symptoms and BMI at ages 8, 12, 14 and 16 years in 2386 pairs of monozygotic twins from the Twins Early Development Study (TEDS); (ii) within- and between-family ADHD and BMI polygenic score (PS) analyses in 3320 pairs of dizygotic TEDS twins; and (iii) two-sample bidirectional Mendelian randomization (MR) using summary statistics from genome-wide association studies (GWAS) on ADHD (N = 55,374) and BMI (N = 806,834).Results: Mixed results were obtained across the three methods. Twin-difference analyses provided little support for cross-lagged associations between ADHD symptoms and BMI over time. PS analyses were consistent with bidirectional relationships between ADHD and BMI, with plausible time-varying effects from childhood to adolescence. MR findings also suggested bidirectional causal effects between ADHD and BMI. Multivariable MR indicated the presence of substantial confounding in bidirectional relationships.Conclusions: The three methods converged to highlight multiple sources of confounding in the association between ADHD and BMI. PS and MR analyses suggested plausible causal relationships in both directions. Possible explanations for mixed causal findings across methods are discussed. [ABSTRACT FROM AUTHOR]

Erotic target identity inversions (ETIIs) are poorly studied paraphilias that involve sexual arousal by the idea or fantasy of being the object of one's sexual desires. To conduct a large non-clinical online survey to investigate self-reported sexual arousal, behavioral expression, and psychological correlates of 4 proposed ETIIs. A total of 736 natal males and 549 natal females responded to items about self-reported sexual arousal to the idea of acting as an animal (autoanthropomorphozoophilia) or the idea of acting as a child or infant (autonepiophilia), natal males reporting arousal to the idea of acting as a woman (autogynephilia), and natal females reporting arousal to the idea of acting as a man (autoandrophilia). Data pertaining to sexual orientation, childhood gender nonconformity, gender identity discomfort, autism, masochism, and humiliation were also collected. The main outcome was a measure of self-reported arousal and expression of the ETIIs being explored using 4 items: arousal level (–3 to 3) when imagining being the erotic target exemplar; frequency of engagement in dressing or behaving like their preferred target (0–4); strength of feeling that they would be better off as the target (0–4); and the frequency of consideration of making physical changes to look or function more like the target (0–4). Mild levels of reported sexual arousal to the idea of being the preferred erotic target were common among the 4 groups, characterizing about half of them. Gender identity discomfort was associated with autogynephilia, autoandrophilia, and autoanthropomorphozoophilia. Greater gender nonconformity was associated with autogynephilia, autoandrophilia, and autonepiophilia. Autism scores were associated with autoandrophilia and autonepiophilia. Masochism was not associated with ETII scores, but humiliation was. Findings suggest that it may be important to distinguish between subgroups of those with different levels and types of ETII arousal/expression. Strengths of this study include the large, non-clinical sample of men and women for the investigation of ETIIs and the inclusion of measures of psychological correlates. The use of an Internet sample with self-report measures may be unrepresentative, although the Internet has the advantage of allowing recruitment from stigmatized or unusual groups. The cross-sectional nature limits our conclusions, as no causal inferences can be made. The results support the concept of ETIIs as a paraphilic dimension in non-clinical samples and the possible role of gender-related psychological factors. Brown A, Barker ED, Rahman Q. Erotic Target Identity Inversions Among Men and Women in an Internet Sample. J Sex Med 2020;17:99–110. [ABSTRACT FROM AUTHOR]

Background: The present study investigated longitudinal associations and bidirectional influences between family members in smoking behavior using a longitudinal full-family design. Family systems provide a powerful social context in which modeling and imitation take place. In current literature, however, bidirectional associations between parents and children in smoking behavior are seldom considered. Methods: Participants were 426 families, including mothers, fathers, and 2 adolescent children. Associations were assessed over 5 waves with yearly intervals using a cross-lagged model in structural equation modeling. Results: Findings demonstrate that families resemble an interactive system affording smoking contagion across family members. Results suggest that associations between parents and children are bidirectional, that is, parental smoking behavior influences adolescent smoking behavior and adolescent smoking behavior influences parental smoking behavior. There is insufficient evidence to conclude that longitudinal associations between family members are generally bidirectional, as only unidirectional longitudinal associations were found between between siblings and partners. Conclusions: The present study extends previous research on the intergenerational transmission of smoking behavior by demonstrating bidirectional influences between parents and children in smoking behavior. Moreover, the present study suggests that family members may be susceptible to adjust their smoking behavior across time in response to smoking behavior within the family. [ABSTRACT FROM AUTHOR]