In a context where psychiatry is experiencing a structural and medical crisis, redesigning patient care areas has become a priority. How can nature be integrated into psychiatric hospitals to promote well-being and healing? This dissertation explores this issue by examining the evolution of psychiatric institutions and medical practices, then highlighting the benefits of nature on mental health. It offers concrete solutions for integrating nature, whether through interior design, creating green spaces or imitating nature indoors. This work seeks to provide design suggestions to create the calming, comfortable and serene environment that is essential for patients' recovery.