Americans with mental illness had good reason to celebrate when the Supreme Court upheld President Obama’s Affordable Care Act. The law promises to give them something they have never had before: near-universal health insurance, not just for their medical problems but for psychiatric disorders as well.

Until now, people with mental illness and substance disorders have faced stingy annual and lifetime caps on coverage, higher deductibles or simply no coverage at all.

This was supposed to be fixed in part by the Mental Health Parity and Addiction Equity Act of 2008, which mandated that psychiatric illness be covered just the same as other medical illnesses. But the law applied only to larger employers (50 or more workers) that offered a health plan with benefits for mental health and substance abuse. Since it did not mandate universal psychiatric benefits, it had a limited effect on the disparity between the treatment of psychiatric and nonpsychiatric medical diseases.

Now comes the Affordable Care Act combining parity with the individual mandate for health insurance. As Dr. Dilip V. Jeste, president of the American Psychiatric Association, told me, “This law has the potential to change the course of life for psychiatric patients for the better, and in that sense it is both humane and right.”