The answer is in the air (atmosphere)...

'Rain, Steam, and Speed - The Great Western Railway' (1844) by William Turner, quoted as saying "Atmosphere is my style"

The creation of 'atmosphere' (not in the weather sense) is probably the answer to creating spaces that provide reassurance, and places for mental health patients to restore their mental health.

The following is taken from:  Atmospheres. On the Experience and Politics of Architecture, edited by Christian Borch, 19-41. Basel: Birkhauser, 2014.

What is 'atmosphere'?

"My central argument is that atmospheres are not only numinous, they are also produced by us, and there are professions whose very tasks it is to produce them. As a result, for me the art of stage-setting became the paradigm for the production of atmospheres, an attempt that you can also find in architecture, marketing, and various strategies of design, as well as in the stage-setting of commodities."
- Gernot Bohme (p91)

"I conceive of atmospheres as spaces...with a mood, or emotionally felt spaces. This is an important definition, because it underlines that emotions do not always have to be in your heart or in your soul, something internal. Emotions can be on the outside, they can strike you." - Olafur Eliasson (p96)

Juhani Pallasmaa describes experiential atmosphere as the whole perceptual, sensory and emotive impression of a space or setting. Atmosphere is the unifying character of a room (or place, or landscape or social encounter). It is an experiential property suspended between the object and the subject.

The intuitive and emotive capacity to sense the atmosphere of a place before we identify any details or process it intellectually is probably the result of evolutionary biology and neurology. It is suggested that we are genetically and culturally conditioned to seek or avoid certain atmospheres. For example, our universal pleasure in being in the shadow of large trees looking out into a sunlit open field can be explained on the basis of evolutionary programming (Edward Wilson. 'The Right Place' in Biophilia: the Human Bond with Other Species, 103-118. Cambridge: Harvard University Press, 1984). The ability to instantly differentiate a scene of potential danger with one of safety implies obvious evolutionary advantages. The main thing to note is that this is not consciously deduced from details but from the scene as a whole.

Smell is a powerful element of atmosphere. Pallasmaa observes that '...the most persistent memory of any space is often its' smell.' (Eyes of the Skin, p54)

Quasi-objective

Atmosphere is not necessarily a wholly subjective or individual experience. A room may produce a certain feeling which is felt more or less similarly regardless of who experiences it. For example, much religious architecture is based on creating an atmosphere of reverence, reflection, quiet spirituality in all who enter the spaces.As such, it assumes a quasi-objective quality. Entering these spaces influences the basic mood of a person entering them.