English: dual diagnosis 
Welsh: diagnosis deuol
Subject: Gwasanaethau cymdeithasol
Welsh definition: Dual diagnosis is the term used to describe patients with both severe mental illness (mainly psychotic disorders) and problematic drug and/or alcohol use. Personality disorder may also co-exist with psychiatric illness and/or substance misuse.
Welsh context: Mae diagnosis deuol wedi’i ddefnyddio fel ffactor o bwys mewn llawer o ddigwyddiadau annisgwyl gan gynnwys hunanladdiad a dynladdiad.