Largest GWAS of PTSD (N=20 070) yields genetic overlap with schizophrenia and sex differences in heritability

The Psychiatric Genomics Consortium-Posttraumatic Stress Disorder group (PGC-PTSD) combined genome-wide case-control molecular genetic data across 11 multiethnic studies to quantify PTSD heritability, to examine potential shared genetic risk with schizophrenia, bipolar disorder, and major depressive disorder and to identify risk loci for PTSD. Examining 20 730 individuals, we report a molecular genetics-based heritability estimate (h2SNP) for European-American females of 29% that is similar to h2SNP for schizophrenia and is substantially higher than h2SNP in European-American males (estimate not distinguishable from zero). We found strong evidence of overlapping genetic risk between PTSD and schizophrenia along with more modest evidence of overlap with bipolar and major depressive disorder. No single-nucleotide polymorphisms (SNPs) exceeded genome-wide significance in the transethnic (overall) meta-analysis and we do not replicate previously reported associations. Still, SNP-level summary statistics made available here afford the best-available molecular genetic index of PTSD-for both European- and African-American individuals-and can be used in polygenic risk prediction and genetic correlation studies of diverse phenotypes. Publication of summary statistics for ∼10 000 African Americans contributes to the broader goal of increased ancestral diversity in genomic data resources. In sum, the results demonstrate genetic influences on the development of PTSD, identify shared genetic risk between PTSD and other psychiatric disorders and highlight the importance of multiethnic/racial samples. As has been the case with schizophrenia and other complex genetic disorders, larger sample sizes are needed to identify specific risk loci.

Post-traumatic stress disorder and cardiometabolic disease: improving causal inference to inform practice

Post-traumatic stress disorder (PTSD) has been declared 'a life sentence' based on evidence that the disorder leads to a host of physical health problems. Some of the strongest empirical research - in terms of methodology and findings - has shown that PTSD predicts higher risk of cardiometabolic diseases, specifically cardiovascular disease (CVD) and type 2 diabetes (T2D). Despite mounting evidence, PTSD is not currently acknowledged as a risk factor by cardiovascular or endocrinological medicine. This view is unlikely to change absent compelling evidence that PTSD causally contributes to cardiometabolic disease. This review suggests that with developments in methods for epidemiological research and the rapidly expanding knowledge of the behavioral and biological effects of PTSD the field is poised to provide more definitive answers to questions of causality. First, we discuss methods to improve causal inference using the observational data most often used in studies of PTSD and health, with particular reference to issues of temporality and confounding. Second, we consider recent work linking PTSD with specific behaviors and biological processes, and evaluate whether these may plausibly serve as mechanisms by which PTSD leads to cardiometabolic disease. Third, we evaluate how looking more comprehensively into the PTSD phenotype provides insight into whether specific aspects of PTSD phenomenology are particularly relevant to cardiometabolic disease. Finally, we discuss new areas of research that are feasible and could enhance understanding of the PTSD-cardiometabolic relationship, such as testing whether treatment of PTSD can halt or even reverse the cardiometabolic risk factors causally related to CVD and T2D.

The Norwich Heat Pump

The paper provides the history and constructional details and working results of what is believed to be the first large heat pump used for building heating in Great Britain. This machine was constructed and installed as an experimental machine for heating a large block of municipal buildings in Norwich.

A brief explanation indicating the principle upon which the heat pump works is given. Reference is also made to the differences between the reversed heat engine when working as a refrigerator and when working as a heat pump. In the latter case there is a deliberate increase in the final temperature T1, from approximately 85 deg. F. to temperatures which may be of the order of 150–200 deg. F. The unsuitability of the term “coefficient of performance”—normally used as a criterion of refrigerator performance—when used as a coefficient relating to the heat pump is pointed out; and the use of a new, alternative term is suggested.

The results are shown of operating the Norwich Heat Pump for two winter heating seasons. When using an unsuitable compressor the heat delivered to the building was found to be 3·45 times greater than the equivalent heat (electric) energy required to operate the machine, averaged over the 1945–6 winter heating season. With a more efficient compressor, installed later in 1946, a still better performance is anticipated. The actual costs of heating the building, with coal-fired boilers and a heat pump respectively, are shown in the form of a table. Conclusions indicated are that the heat pump can show a financial saving, as compared with the use of coal-fired boilers, and that it is practicable to use the heat pump in Great Britain for building heating throughout normal English winters.