Dr. Liam Mac Gabhann:

Historically, dual diagnosis was a diagnostic term developed because of the issues with people having comorbidity, perhaps addiction and mental illness, using a really strong medical term. There were also cultural reasons that people fell through the gaps because right across the western world, people had different kinds of services responding. The hope was that by bringing together a dual diagnosis, people would be seen in all their complexity. However, cultures throughout the world and particularly here in Ireland, still managed to separate those and call them two diagnoses. This allowed for people to continue to fall through the gaps and for different service orientations to be able to say "No, not on my doorstep".