- The document discusses dual diagnosis, which is when a person has both a substance misuse issue and a mental health disorder. It is common for the causes and symptoms to overlap. - Dual diagnosis is a major issue, with around 3/4 of prisoners and 75-80% of drug/alcohol service users also experiencing mental health problems. Only 62% of drug users with mental health issues receive treatment. - Having both a substance use disorder and mental illness leads to worse health outcomes and difficulties accessing care. The document advocates for services to better coordinate and meet people's full range of needs.