Even before the COVID-19 crisis, America’s infrastructure for mental-health and addiction services was fragmented, overburdened, and underfunded. The coronavirus has put far more stress on that broken system. So far, Congress has failed to shore it up. That oversight will prove harmful to patients and their families and costly to insurers and taxpayers. Mental-health disorders were already at the top of the list of the most costly conditions in American health care even before COVID-19.