(FORTUNE Magazine) – Over more than a century, in roughly 30-year cycles, psychiatry has embraced one popular class of drugs after another to treat mental illness. At first, they have seemed to be miracle workers--but they have usually turned out to be risky.

COCAINE

In 1884, a young Freud writes "Über Coca," an ode to "this magical substance" that, he says, can be used to treat depression and even morphine addiction.

AMPHETAMINES

Starting in 1937, amphetamines are available over the counter to treat nasal congestion. During World War II, soldiers take speed to stay alert and improve their moods.

BARBITURATES

In their 1950s and '60s heyday, about 50 types of barbiturates are marketed for medical use. In 1962, Marilyn Monroe dies from an overdose.

VALIUM

In 1978, users pop 2.3 billion Valiums. The drug's ubiquity is immortalized in Jacqueline Susann's novel Valley of the Dolls, later made into a movie starring Patty Duke.

PROZAC

The FDA approves Prozac for use in 1987, and within three years annual sales near $800 million. In 1993 psychiatrist Peter Kramer's Listening to Prozac is a nonfiction bestseller.