• Assertive Community Treatment (ACT) Assertive Community Treatment (ACT) is a community-based approach to comprehensive assertive team treatment and support for adults with serious mental illness. Services are targeted to a specific group of individuals with serious mental illness, ACT team members share responsibility for the individuals served by the team, the staff to consumer ratio is at least 1:10, the range of ACT treatment and services is comprehensive, interventions are carried out in vivo rather than in clinic or hospital settings, and services are individualized.