Assignment 1: Environmental Effects on Mental Health Worksheet

We conducted a cross-sectional analysis using same-sex twin pairs from the University of Washington Twin Registry (UWTR), 2008–2014. Twins completed a brief recruitment survey on initial contact, and a follow-up survey in 2010. Both surveys collected information on sociodemographics, health behaviours, and health conditions. A total of 4338 twins were included in this study. 

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This study consists of 4338 same-sex twin pairs in a cross-sectional analysis from the University of Washington Twin Registry, 2008-2014. The twins provided information on their sociodemographics, health behaviours and health conditions on a brief recruitment survey on initial contract (2008) and a follow up survey in 2010.

The aim of this study was to establish the association between access to green space and

mental health among and within adult twin pairs. We hypothesised that greater access to

green space would be associated with better mental health outcomes, controlling for genetic

and shared environmental confounds within twin pairs.

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The introduction establishes that the purpose of this study was to determine whether having greater access to green space is related to better mental health in the 4338 same-sex adult twins. The researchers expect that people with more access to green space would have better mental health, even after accounting for genetic factors and environmental experiences shared by the twins.

The sample included 4338 twins; NDVI ranged from 0.08 to 0.89, with a mean of 0.57 (SD

0.15), indicating moderate to high vegetation density. Twins who lived in greener areas

tended to have higher annual incomes, and were less likely to identify as Hispanic/Latino or

to use transit. Greener areas were more likely to have lower Singh Index scores and lower

population density.

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Out of the total 4338 twins, there was a significance in the overall mental health for the twins that lived in greener areas. Those twins tended to have higher incomes, not self-identify as Hispanic/Latino, not rely on public transportation and tended to live in less dense neighbourhoods.

This study supports the hypothesis that greater access to residential green space is associated

with less depression, but provides less evidence of an association between green space and

stress or anxiety. Each of the three phenotypic models showed significant inverse

associations between green space and mental health. However, only the association with

depression remained significant in within-pair (monozygotic, MZ) univariate and adjusted models.

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The hypothesis of this study is supported that greater access to green space near their homes tended to have lower levels of depression; however, there is not enough evidence to say that is there is an association between green spaces and stress or anxiety. When identical twins were compared, the connection between green spaces near their homes and lower rate of depression was the only result that remained significant.

Researchers should evaluate the quantity/density of the available green space that could play in a role in each twin. They should also follow the twins for a longer period time to see what type of green spaces (and how much) is improving their mental health. Also, the participants should submit how much they’re spending outdoors in their local neighbourhoods and enjoying their green spaces. Physical activity and social factors also play in the role if a twin is potentially sharing the green space and their time with their other twin or other loved ones.

I think what I found hard to understand was understanding the different measures under Materials and Methods , there was “ Exposure measure”; “Outcome measures”; “Covariate measures”; “Statistical analysis”. In the “Statistical analysis” (not my strongest subject anyways) but they listed the a statistical model to take full advantage of the twin design but I would have on how to fill it in if it wasn’t for the brief explanation after.