The report compared the happiness levels of 200 tenants renting properties from a housing charity. Half of those questioned had high levels of nearby tree cover and half had few or no nearby trees.
The results showed that even with other factors broadly the same, tenants with high nearby tree cover had higher happiness scores than those with few or no trees in their area.
In particular, tenants with nearby trees were more likely to say they were feeling relaxed and were thinking clearly than those with no trees, the report found.
The properties used in the study had waiting lists, so tenants were assigned their flats depending on when they became available. This resulted in a random allocation of tenants, who had no particular relationship to trees or nature, and therefore provided the advantages of a near-randomised trial, such as those used in scientific tests, according to the researchers.
Author and tree consultant Adam Winson said: "In recent times, a lot of attention has been given to improving mental well-being or 'happiness', and people have often thought that nearby trees in our towns and cities were good for our happiness levels."
He added: "This research attempted to test this idea. The results of the study show that our urban trees are not just something to make an area look nice but they may actually be making people happier."