This dissertation presents a systematic, integrated approach to the design and development of an evidence-based sensory supportive assistive technology for people with mental illness. A systematic integrated design approach and a set of modified design decision-making tools has been developed based on principles and theory of traditional engineering and design of assistive technologies. Specifically, the research provides a vehicle to quickly and successfully go from bench top to bedside and back by systematically integrating fundamental scientific discoveries, market research, and technology research and development in a rigorous and traceable way. An evidence base for the use of weighted blankets, weighted vests, and the novel deep pressure application system has been developed. Ten IRB approved human subjects studies, including pilot studies, with approximately 250 human subject participants were conducted. The studies collected a range of measures to explore safety, efficacy, function, design, research methodologies, and in situ protocols. The populations studied included typical adults, acute mentally ill adults in a locked mental health care facility, typical adults under stress, children with autism, and experts in the fields of research and use of DPTS modalities. These studies required the integration of multiple disciplines including engineering, nursing, occupational therapy, psychology, speech language pathology, entrepreneurship, and marketing. Through the implementation of the integrated design process and decision support tools, a novel deep pressure application system was developed: DeePAD. DeePAD was based on the scientific findings, responses, and experience gained from integrated clinical research studies. DeePAD has been verified to function in situ and has been verified to be adoptable. The Braided design approach and modified Pugh’s Method decision-making tools have resulted in the first critical step from general design principles and guidelines to a systematic integrated and traceable early stage design innovation methodology. This integrated multidisciplinary design approach has overcome the heterogeneity across cognitive, social, behavioral, and communication domains of people with mental illness while providing a ‘single user’ experience, thus reducing the risk of abandonment. This work is the first to provide design engineers a systematic, integrated design approach to develop adoptable evidence-based sensory supportive assistive technologies for people with mental illness and pervasive developmental disorders.