This article says that teenagers in green environments are less aggressive, even after controlling for socioeconomic factors.
The researchers describe several “possible pathways” that could explain their results. Easy access to the natural world may reduce maternal stress, which can lead to children acting out. It can encourage physical activity, reduce air pollution levels, and “act as a buffer for ambient noise.”
In addition, they write, green space in urban areas has been shown to preserve “the microbial biodiversity needed to drive immunoregulation, and to optimize brain health.”