We may never know whether television is better at curing depression or causing it. An "I Love Lucy" rerun can be a pretty effective pick-me-up, and yet at other times, the punishingly mechanical banality of television seems only to amplify feelings of loneliness and alienation.

Tonight, a special edition of the ABC News magazine "20/20" called "Depression: Beyond the Darkness" devotes an entire hour to the study of depression and current methods of treatment. Unfortunately, Washington's dismal ABC affiliate, WJLA (Channel 7),has preempted the report for a preseason football game, and a station spokesman said yesterday there were no plans to show it. That is depressing.

Many area viewers, however, will be able to see it via Channel 13 in Baltimore at 10 p.m.

Hugh Downs adroitly anchors the report, and while depression is described in such lurid hyperbole as "torment," "sheer horror" and "excruciating agony," viewers are also told that "most cases can be successfully treated."

The problem, or one of the problems, is that only one in three Americans suffering from depression seeks that treatment. ABC's program, written and produced by Jonathan Talmadge, urges those who think they have the symptoms to consider professional help.

"I'm so empty, I can't even cry," wrote a long-depressed college student before taking his life at the age of 19. A woman asked to describe her depression says, "It's like hell," and another, asked to name the last time she was happy, responds with a long, long pause followed by "I can't answer that."

A 12-year-old boy suffering from depression says he first considered suicide at the age of 10.

This isn't just the blues, or the grumpiness that can come from five rainy days in a row. It's a serious illness, and so are the treatments. A postal worker undergoes shock therapy -- on camera -- and later is seen at home, smilingly pronouncing it a success.

Shock treatments have changed since first introduced in the '30s, Downs says. A film clip of Jack Nicholson simulating one in "One Flew Over the Cuckoo's Nest" is contrasted with the real thing as it occurs today. Now patients get muscle relaxants that virtually bliss them out.

But every therapy has its attendant debate. "It's like a lifetime disappeared," says a depressed woman who lost much of her memory after 20 shock treatments blasted it away. A psychiatrist says shock therapy may not look as barbaric as it used to, but still is.

Then there's Prozac, the chic new drug that U.S. doctors write 650,000 prescriptions for every month. It epitomizes a new pharmacological approach to treating depression, as opposed to the old way, which often involved spilling out one's guts to a shrink. "The pill has replaced the couch," one doctor declares.

A young woman on Prozac says she feels "ten million times" better since therapy began, and an insurance agent whose depression got so bad that, he says, "I died somewhere" now takes Prozac, paints, fishes and testifies, "I'm rebuilding, rebuilding."

Lawsuits have been filed by a few patients who claim Prozac induced violent suicidal thoughts. But none of these cases has been decided in court, and "Darkness" seems balanced in the way it deals with the issue. Unfortunately, Eli Lilly & Co., manufacturer of the drug, stuck to its shortsighted policy of refusing to comment on the controversy. That only makes it look guilty -- as any corporate public relations department ought to know by now.

Writer William Styron, profiled in a related piece on Thursday's "PrimeTime Live," had to be hospitalized for depression. "A cloud had descended over my mind," he says. Therapy cured him, however, and now he feels as though he has gone through "rebirth."

"20/20" is one of the great TV success stories that rarely get written about. In truth, some of the show's weekly features have been unforgivably glib and shallow. But it has also achieved excellence. "Beyond the Darkness" is definitely in the latter category.

It's too bad the program doesn't investigate some of the aspects of modern American life that have caused what appears to be a rise in cases of depression -- or is it just that we've become better at labeling things as diseases?

In addition, some of the video is a trifle arty, and sessions between psychiatrists and patients appear to have been shot in a TV studio. The camera pans ominously to a shadow on a wall behind a depressed man; this was probably mapped out in advance.

Still, the potential for the program actually to be of positive use to people is considerable, and for all the hyperbole about the "insidious" nature of the disease, time and again we are told that most people can indeed be helped. The "darkness" can be vast, but it is not necessarily impenetrable.