Answer : A variety of fields support interior decoration. One area of particular interest is architecture, as it can provide the foundation for a space in terms of layout and feel. However, interior designers must also be knowledgeable about color theory, textile design, furniture design, and more in order to create an immersive and aesthetically pleasing experience for their clients.
It's also worth noting that the field has expanded in recent decades to encompass more specialties such as event planning, healthcare design, and hotel design. So there really isn't one specific field that "supports" interior decoration - it's more accurate to say that a variety of fields intersect to create this multidisciplinary industry.