RESUMEN
Previous cross-sectional studies suggest that birth weight (BW) is associated with aggression-, social- and attention problems differently in boys and girls. We sought to test if these differences could be confirmed in a longitudinal study. The 1989 Raine Study provided prospectively collected data on perinatal variables and repeated child behaviour checklist assessments from ages 5 to 17. Linear mixed effects models provided crude and adjusted relationships between BW and childhood behaviour at a conservative significance threshold using prenatal maternal covariables in adjusted models. Sensitivity analyses included an age10 teacher assessment. Data on behaviour, BW and sex, was available in 2269 participants. Male sex was associated with increased aggression problems at lower BW compared to females in the crude model (Interaction B: -0.436, 98.3%CI: [-0.844, -0.0253]), but not the adjusted model (Interaction B: -0.310, 98.3%CI: [-0.742, 0.140]). Male sex was associated with increased attention problems at lower BW compared to females in both the crude model (Interaction B: -0.334, 98.3%CI: [-0.530, -0.137]) and the adjusted model (Interaction B: -0.274, 98.3%CI: [-0.507, -0.0432]). Male sex was associated with increased social problems at lower BW compared to females in both the crude model (Interaction B: -0.164, 98.3%CI: [-0.283, -0.0441]) and the adjusted model (Interaction B: -0.148, 98.3%CI: [-0.285, -0.00734]). Using repeated measures from ages 5-17 we were able to show a crude and adjusted male vulnerability to lower BW in the development of attention problems and social problems. We did not find a BW x sex interaction for the development of aggressive behaviour.
RESUMEN
OBJECTIVES: Bipolar disorder is associated with increased body mass index (BMI), but it remains undetermined if this association is causal and, if so, in which direction it goes. Here, we sought to answer these questions using bidirectional two-sample Mendelian randomization, a method from genetic epidemiology that uses data from genome-wide association studies (GWAS) to examine whether a risk factor is causal for an outcome METHODS: We used summary statistics from GWAS of bipolar disorder and BMI conducted using data collected by the Psychiatric Genomics Consortium and the UK Biobank, respectively. The genetic instrument for bipolar disorder contained 53 SNPs and explained 0.5% of phenotypic variance, while the genetic instrument for BMI contained 517 SNPs and explained 7.1% of phenotypic variance RESULTS: Our findings suggest that genetic liability to bipolar disorder reduces BMI (slope from Egger regression = -0.195, p = 0.004). It follows that a twofold increase in the genetic liability to bipolar disorder leads to a 0.6 (kg/m2 ) reduction in BMI, predominantly driven by reduced fat mass. Conversely, we found no evidence that BMI causes changes in the risk of developing bipolar disorder CONCLUSION: The results of this study suggest that the increased BMI observed among individuals with bipolar disorder is not a direct consequence of genetic liability to bipolar disorder, but may more likely represent the sum of downstream correlates of manifest bipolar disorder, such as side effects of pharmacological treatment, poor diet, and sedentary lifestyle. As these factors are all modifiable, they can be targeted as part of clinical management.
