Only the real deal? Actual vs. virtual nature exposure and their effects on affect and cortical hemodynamics in health and major depression.

Exposure to natural environments promotes mental health, but access is often limited. Virtual nature-based interventions may offer an alternative, yet direct comparisons of their affective and neurobiological effects with actual nature remain scarce, particularly in depression. To elucidate these effects, thirty-two patients with major depressive disorder and thirty-two healthy controls participated in a quasi-experimental comparison of 10-minute natural and urban exposure in actual or virtual reality (immersive 360° videos via head-mounted display). Actual-exposure data were obtained from an earlier cohort and virtual-exposure data from subsequently recruited participants, with pseudorandom assignment to nature versus urban exposure within each modality. Affective and psychological outcomes were assessed using standardized questionnaires, cortical hemodynamics using portable functional near-infrared spectroscopy (fNIRS), and salivary cortisol as a stress marker. We found that both actual and virtual nature induced positive psychological effects, but only actual nature significantly reduced negative affect. We observed significant region-dependent differences in cortical hemodynamics, with exploratory analyses suggesting reduced dynamics during actual nature exposure in prefrontal and temporal regions, which however did not survive multiplicity correction. Cortisol showed no differential nature-versus-urban trajectories. Exploratory analyses suggested that the affective benefits of virtual nature correlated with the subjective sense of presence. Effects did not significantly differ by diagnostic status. However, given the modest sample size, these findings should be regarded as exploratory. They provide preliminary evidence that actual nature exerts differential effects on affect and cortical hemodynamic responses, while optimizing presence may enhance the efficacy of virtual nature-based interventions.