Beyond Sight and Sound: A Systematic Review of Haptic and Olfactory Feedback in Therapeutic Virtual Reality Interventions

Across a range of psychological challenges, virtual reality (VR) integrating multiple sensory modalities holds significant promise for mental health interventions. Among other senses, our sense of touch and smell play a critical role in emotional processing and could enhance therapeutic outcomes when implemented into immersive environments. However, the potential of therapeutic VR experiences is currently limited by the underutilization of haptic and olfactory feedback, despite their strong influence on user perception and emotional states. This systematic review synthesizes findings from 39 studies, examining the impacts and challenges of integrating haptic sensations and olfactory cues into immersive VR environments for therapeutic interventions, including exposure therapy for PTSD, anxiety management, stress reduction, depression treatment, relaxation, and related mental health conditions. Our analysis reveals a growing trend in haptic feedback utilization for presence and immersion, while olfactory integration in therapeutic simulations remain considerably less developed, despite its known capacity to evoke strong emotions and vivid memories. Notably, our paper highlights a substantial research gap on the combined use of both haptic and olfactory stimuli, specifically in the context of therapeutic VR interventions. By identifying current gaps, trends, and challenges in multisensory integration, our goal is to establish a foundation for future research aimed at creating emotionally engaging mental health interventions and optimizing the delivery of haptic and olfactory modalities within VR experiences for enhanced therapeutic efficacy.