Instant Message-delivered Personalised Acceptance and Commitment Therapy (IMPACT) for Neuropsychiatric Symptoms in Persons With Mild Cognitive Impairment

1. Message contents: The message content library will consist of two parts: 1. brief mild cognitive impairment messages (optional), and 2. acceptance and commitment therapy messages (mandatory). 2. Message delivery * Regular messages: The messages in the two parts will be sent regularly to each participant. As personalisation is a core process subject to behavioural changes, the content, frequency, and timing of the messages will be determined based on participants' preferences. To save labour and increase efficiency, the investigators will develop a message 'scheduler' program. The investigators will pre-set the message scheduler, which will then automatically send out content to the participants according to their preferences. The development of the program is highly useful particularly in cases which participants prefer to receive messages during non-office hours. * Real-time support messages (chat-type): Chat-based support will be given to the participants as an extension of the regular messages. However, the participants will be informed beforehand that the RA will only play a supportive role and will not provide formal care. The number of the chat messages will not be limited, but the real-time support messages will only be provided during working hours (i.e., 9am-10pm) on weekdays to limit the RA's workload. Control Group: The control group will receive instant messages about mental health management from GovHK website (https://www.gov.hk/en/residents/health/mental/), which is open to the public.