A possible synonym for “asylum patient” could be “mental health institution resident”.
This term emphasizes the fact that the person is residing in a specialized institution for mental health care. For example, “The mental health institution resident was receiving therapy and support.” It shows that the individual is in a place dedicated to addressing their mental health needs.
Another synonym could be “psychiatric facility client”. “Client” implies a relationship where the person is receiving services. For instance, “The psychiatric facility client was participating in group therapy sessions.” This indicates that the person is being cared for in a facility focused on mental health.
“inpatient at a mental asylum” is a more traditional synonym but might be considered less politically correct in modern usage. However, it still conveys the idea of someone being housed and treated in a specialized institution. For example, “The inpatient at a mental asylum was under the care of professional psychiatrists.”