Senator Amy Klobuchar on Friday released a $100 billion plan to combat drug and alcohol addiction and improve mental health care, focusing one of the first detailed proposals of her presidential campaign on an issue deeply personal to her.

Ms. Klobuchar — who has spoken before about her father’s alcoholism, including memorably at Justice Brett M. Kavanaugh’s confirmation hearing — said she had developed the plan and made it an early focus in part because of that personal experience and in part because of the number of addiction-related stories she had heard from voters.

The bulk of the plan is divided into three segments.

• Prevention, including funding for mental health programs at schools, training for doctors to recognize early warning signs of addiction and other mental health problems, and a requirement that doctors use prescription drug monitoring programs intended to prevent “doctor shopping,” in which patients addicted to opioids receive new prescriptions from a number of doctors.

• Treatment, including funding for addiction and mental health programs and stricter enforcement of the Affordable Care Act’s requirement that insurers cover mental health care. The plan highlights in particular the need for more hospital beds and community clinics, especially in rural areas: Some of the counties hit hardest by the opioid crisis are rural, and many of them have no psychiatrists.