Based on the 2018 National Survey on Drug Use and Healthi, approximately 47.6 million adults (18 and older) had a mental illness in the past year, with an estimated 11.4 million adults having a serious mental illness (SMI). There is also an increasing percentage of those with mental health issues who also have a substance use disorder (SUD); approximately 9.2 million adults had both mental illness and a SUD in the last year.