This study presents a systematic literature search and narrative meta-review of the current state of research on conversational agents (CAs), including embodied CAs, chatbots, and social assistive robots (SARs). The investigation identifies 1,830 academic articles, of which 315 articles satisfied the inclusion criteria for the review. Systematic reviews across various fields are reported, including mental disorders, neurodevelopmental disorders, dementia/cognitive impairment, other medical conditions, elderly support, health promotion, mental health, education, industrial applications, agent characteristics, and robot characteristics. The study highlights challenges in current CA research, such as the scarcity of high-quality comparative studies and the acceptance of CAs by users and caregivers, particularly in elderly support. The article also categorises ethical discussions into nine elements: privacy, safety, innovation, user acceptance, psychological attachment, care philosophy, evaluation, social systems compatibility, and rule development. It also offers insights into the development of future guidelines. The role of CAs in fostering human relationships through their conversational function is emphasised to provide guidance for subsequent CA research and social implementation. As advancements in CA technology and research continue to progress, there is an increasing demand for sophisticated psychological investigations addressing relationships, emotions, and the self.
