Background: For ICD-11, the WHO emphasized the clinical utility of communication and the need to involve service users and carers in the revision process.
Aims: The objective was to assess whether medical vocabulary was accessible, which kinds of feelings it activated, whether and how users and carers would like to rephrase terms, and whether they used diagnosis to talk about mental health experiences.
Method: An innovative protocol focused on two diagnoses (depressive episode and schizophrenia) was implemented in 15 different countries. The same issues were discussed with users and carers: understanding, feelings, rephrasing, and communication.
Results: Most participants reported understanding the diagnoses, but associated them with negative feelings. While the negativity of "depressive episode" mostly came from the concept itself, that of "schizophrenia" was largely based on its social impact and stigmatization associated with "mental illness". When rephrasing "depressive episode", a majority kept the root "depress*", and suppressed the temporal dimension or renamed it. Almost no one suggested a reformulation based on "schizophrenia". Finally, when communicating, no one used the phrase "depressive episode". Some participants used words based on "depress", but no one mentioned "episode". Very few used "schizophrenia".
Conclusion: Data revealed a gap between concepts and emotional and cognitive experiences. Both professional and experiential language and knowledge have to be considered as complementary. Consequently, the ICD should be co-constructed by professionals, service users, and carers. It should take the emotional component of language, and the diversity of linguistic and cultural contexts, into account.
Keywords: Carers; Clinical utility; Communication; International Classification of Diseases; Participatory research; Service users.