Serious Mental Illness Mental Health Apps Market by Operating System (iOS, Android and Others), by Subscription Model (Monthly and Yearly) by Mental Health App Types (Serious Mental Illness Apps, Mental Disorder Apps, Substance-use Disorders Apps, Co-occurring disorders Apps, Co-existing disorders, Others); By Region (U.S., (Northeast, Midwest, West and South)) Insights, Growth, Size, Comparative Analysis, Trends and Forecast, 2019 - 2027