The article is:
https://jamanetwork.com/journals/jamanetworkopen/fullarticle...As a correlational study, and as with any study like this I'm worried that something they're not controlling for, or not sufficiently controlling for, is the actual cause. They say:
> Self-rated health, depression, anxiety, and risk of psychological distress have been previously shown to be associated with green space in some cross-sectional and longitudinal studies. A range of socioeconomic and demographic factors are likely to confound these associations by contributing to mental health outcomes and to neighborhood selection. Previous research suggests that these factors are likely to include personal socioeconomic circumstances, such as how much money people have, whether they are employed, and their level of education, and other factors, such as age, sex, and relationship status. Accordingly, in this study, we adjusted for baseline measures of age, sex, annual household income, economic status (eg, employed, retired, or unemployed), highest educational qualification, and couple status.
There are a lot of measures that affect human wellbeing that this doesn't take into account, however. For example, wealth and class aren't present. I understand why it would be hard for them to adjust for everything, but that also makes the study much less predictive.
I wonder if there are any natural experiments we could look at where blights or storms that caused sudden reductions in tree cover in a mostly independent fashion?