Green space exposure predicts manic episodes in bipolar disorder: one year longitudinal analysis using smartphone-derived GPS data

Urban living is linked to increased psychiatric morbidity, while green spaces may protect mental health
via stress-buffering effects. Yet, the role of green space exposure in the onset of affective episodes in
bipolar disorder (BD) remains unclear. Using 12 months of GPS data from 29 participants with BD-I/II,
we quantified daily exposure to green spaces (green area & NDVI; covariates: population density &
imperviousness). Affective status (euthymia, depressive or (hypo)manic episode) was assessed via
SCID-based biweekly clinician interviews (26 assessments per participant). Multilevel logistic
regression examined moving averages and temporal variance of green space exposure during
prodromal and episode weeks relative to euthymia. Reduced mean green space exposure and
increased exposure variability were consistently associated with prodromal phases of (hypo)manic
episodes, with variance effects persisting into acute (hypo)mania. In contrast, depressive episodes
showed limited prodromal predictability. These findings suggest dynamic environmental signatures
consistent with early-warning dynamics as modifiable contextual correlates in BD.