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Science Policy Around the Web – December 02, 2016

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By: Liu-Ya Tang, PhD

Source: pixabay

Public Health

Childhood Bullying and Adult Overweight

Bullying is, without a doubt, a big problem in U.S. schools, as “40% to 80% of school-age children experience bullying at some point during their school careers” according to the American Psychological Association. What influence will bullying have on child development? Bullying can not only affect mental health, but also have a lasting effect on a person’s physical health. A recent study finds that bullied children were more likely to be overweight than non-bullied children at age 18.

Scientists studied a cohort of twins from 2,232 children who were followed to age 18. Bullying victimization was reported by mothers and children during primary school and early secondary school. At ages 10, 12 and 18, they collected data for indicators of overweight. To index genetic and fetal liability to overweight, co-twin body mass and birth weight were also used. They found that the association between childhood bullying victimization and being overweight at age 18 was influenced by the chronicity of exposure, as children bullied in both primary school and secondary school showed the highest risk of being overweight. They also measured whether childhood psychosocial risk factors (socioeconomic disadvantage and food insecurity) contributed to a higher risk of being overweight at age 18. To their surprise, the result showed that the elevated risk of bullied children becoming overweight is independent of their psychosocial risk.

The researchers further dug into the mechanisms of why childhood bullying puts kids at high risk for being overweight as a young adult. One possible reason is the allostatic load theory prediction, which states that “more chronic exposure to psychosocial stress is associated with the greatest metabolic abnormalities”. This theory has been supported by a study, in which they found that children being bullied may eat more due to impaired inhibitory control over feeding linked to prefrontal cortex abnormalities. In addition to explanations from the biological aspect, social mechanisms may also need to be taken into account. Bullied children may avoid participating in group sporting activities to reduce the risks of victimization from peers. It is important for school, clinical practice and public health agencies to identify the mechanisms and develop anti-bullying interventions, which could support bullied children to have a healthy life later and help reduce the large public health burden due to overweight. (Jessie R. Baldwin et al., Psychosomatic Medicine)

Climate Change

Will Climatic Warming Affect Soil Respiration?

It is estimated that nine times more carbon dioxide (CO2) is released from soils to atmosphere via soil respiration annually when compared with anthropogenic emissions. This efflux of carbon from soils is attributed to both plant root respiration and microbial respiration. Rising temperatures are expected to increase rates of soil respiration, which potentially provides a positive feedback to climatic warming. However, there were discrepancies in the observations from recent years, so the interaction between soil respiration and climate warming remains uncertain in climate projections.

To understand the complex relationship between soil respiration and temperature, 43 researchers from the United States and Europe conducted a global synthesis of 27 experimental warming studies spanning nine biomes, which results in >3,800 observations. There are numerous interesting findings. With the exception of boreal forest and desert, they didn’t observe significant differences in the temperature sensitivity of soil respiration between warmed or control treatments within other biomes (temperate forest, northern shrubland, southern shrubland, grassland and temperate agriculture). This finding suggests that acclimation of soil communities to warmer conditions is likely to have a greater impact for soil carbon dynamics in boreal forest and desert systems, while climatic warming will have little effect on other biomes. They also investigated the relationship between soil moisture, respiration rate and temperature, and found that the magnitude of the respiration response to warming decreased linearly with the degree of soil drying across the entire dataset.

Interestingly, they found a universal decline in the temperature sensitivity of respiration at soil temperature >25°C for non-desert biomes, while deserts have a higher temperature threshold at 55°C for reduced respiration. The significant difference in soil respiration in response to temperature could be due to a number of factors, such as different plant and microbial communities in the desert compared with other biomes, or abiotic decomposition as a major component of litter decomposition in deserts. Compared with lower latitudes, higher-latitude sites more often experience soil temperature <25°C, where soil respiration rates correlate positively with temperature. So higher attitudes will be more responsive to warmer temperatures. This study helps project future shifts for different geographic regions with the climatic warming. (Joanna C. Carey et al., PNAS)

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Written by sciencepolicyforall

December 2, 2016 at 11:51 pm

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