Mental health data showed that the people who moved to greener locations were a happier lot. "Moving to greener urban areas was associated with sustained mental health improvements, suggesting that environmental policies to increase urban green space may have sustainable public health benefits," said Mathew P. White, lead author of the research.

Mental well-being is a major public health issue across the world, with unipolar depressive disorder being the leading cause of disability in middle to high-income countries, said the study funded by the Economic and Social Research Council, Britain's leading research and training agency addressing economic and social concerns.

Part of the blame for this unhappiness lies in increased urbanisation - nearly 80 percent of the world's population in more developed regions live in city environments, which tend to have little room for nature, said the study appeared in the journal Environmental Science & Technology.