The group New Script for Mental Health says it is trying to build a better understanding of and approach to mental health in Northern Ireland.
Its spokesperson, Lisa Morrison, said the lack of available statistics is a form of “neglect” of people with mental health challenges.
“We don’t have monitoring figures including how many are taking medication for psychotic behaviour, the effectiveness of that medication and crucially what is available for people apart from medication,” she said.
In England an antipsychotic prescribing report is published each quarter, meaning health organisations there can share information about the impact of the medication and who in the community requires follow-up appointments.
Ms Morrison described the lack of that type of data in Northern Ireland as “unacceptable”.
She added that it makes it: “Difficult to assess anything about the prevalence, the impact of and the range of services out there to support men and women dealing with psychosis”.