Within-dwelling density and mental health among adults in Hong Kong : a moderated mediation model of perceived crowdedness and indoor plants

Abstract

In Hong Kong, the negative impact of overcrowded housing on mental health has been a pressing issue. Exposure to indoor plants in various high stress environments have demonstrated overwhelmingly positive physical and psychological outcomes, but the effects have yet to be investigated in home environments. The present research investigated the restorative potential of indoor plants on mitigating perceived crowdedness in home environments and occupants’ stress levels through a mixed methods design consisting of three studies. Study 1 measured the dwelling density of participants’ homes, perceived crowdedness and stress levels for 303 adult residents in Hong Kong via an online cross-sectional survey. The data tested a proposed model that perceived crowdedness mediates the impact of dwelling density on stress. The model was further examined with two moderators, plant presence (Study 1) and plant health (Study 2). Study 3 was an experimental intervention in which a subset of non-plant owning participants from study 1 were randomly assigned to spend 5 minutes actively interacting with a provided plant or non-plant stimulus daily for two weeks. Perceived crowdedness and stress levels were measured post-intervention. Results from Studies 1 and 2 found perceived crowdedness significantly mediating the impact of dwelling density on stress, especially in highly dense homes. The presence of indoor plants in the living space, particularly thriving ones and in homes that are less dense, were also shown to significantly buffer the impact of perceived crowdedness. Although no significant stress-reduction was found in Study 3, most participants in the plant group expressed improved mood after the intervention. Given that the mechanism between dwelling density, perceived crowdedness and stress operate differently across high and low density housing, more research is required to better understand this for people in overcrowded or inadequate housing.