Table 5.

Evaluated design principles for PACAs

#	Title	Design Principles (DPs)
DP1	Principle of Proactive Support	For designers and developers to design personality-adaptive conversational agents (PACA) that provide mental health services to socially support patients independently of therapist, location and time, ensure that the PACA is accessible 24/7 and proactively checks in on the user on a mutually agreed regular basis, so they can receive support at any time.
DP2	Principle of Competence	For designers and developers to design personality-adaptive conversational agents (PACA) that provide mental health services to socially support users independently of therapist, location and time, provide the PACA with a domain-specific knowledge base and incorporate therapeutic techniques, so the user feels understood and perceives the PACA as competent.
DP3	Principle of Transparency	For designers and developers to design personality-adaptive conversational agents (PACA) that provide mental health services to socially support patients independently of therapist, location and time, ensure that the PACA is transparent in communicating patient safety and privacy issues, so that users trust the PACA with their health-related concerns and feel safe when sharing sensitive data.
DP4	Principle of Social Role	For designers and developers to design personality-adaptive conversational agents (PACA) that provide mental health services to socially support users independently of therapist, location and time, allow users to choose between different social roles (e.g., friend, therapist etc.) so the PACA can dynamically take on the user’s preferred social role, but can also switch between social roles that promote the user’s therapy progress.
DP5	Principle of Anthropomorphism	For designers and developers to design personality-adaptive conversational agents (PACA) that provide mental health services to socially support users independently of therapist, location and time, allow the users to choose the type of PACA they want to interact with (chatbot, voice assistant, embodied conversational agent), so they can determine the PACA’s degree of anthropomorphism based on individual needs.
DP6	Principle of Personality Adaptivity	For designers and developers to design personality-adaptive conversational agents (PACA) that provide mental health services to socially support users independently of therapist, location and time, imbue the PACA with language cues specific to different personality dimensions to enable the PACA to adapt to the user’s preferred personality and increase interaction quality.