Depression doesn't have a time schedule. Manic feelings come and go like thunderstorms. Fear and sadness and pain can paralyze at any moment.

During the holiday season, these troubles are not only more prevalent, they're also more acute, according to experts.

Last year, some 400,000 people turned to an unusual Web site called Walkers in Darkness. Developed by Howard County resident Mark Oberg, the site is designed for people with clinical depression or bipolar disorder, but it's open to anyone seeking help for emotional distress.

The site offers information on mental illness, links to helpful sites and a number of chat rooms, where visitors can discuss their concerns. One might call it a virtual support group that runs round the clock.

"It's almost an immediate response," said one Walkers user, known as Hopper, from Cleveland, during a telephone interview. "There's somebody out there that knows exactly how you're feeling."

Availability and anonymity contribute to the site's success.

"It's a lot easier to go to a Web site and post a message and get some feedback than it is to get in the car and drive to a [support group meeting] where you don't know who you're going to run into," said Oberg, 43.

At any given moment on www.walkers.org, one may find a discussion between a woman who's struggling to complete her college degree after years of debilitating depression and another who just got back on her feet after a similar ordeal. Or a nurse from New York trying to cope with the effects of Sept. 11. Or a woman seeking advice about contacting family members during the holidays, hoping to make up for past mistakes.

They may live here in Columbia or California or New Zealand or anywhere in between.

"It is a community even though we never see each other," Oberg said.

And it is one that Oberg himself relies on. A decade ago, while vice president of a now-defunct Columbia high-tech firm, Oberg suffered a breakdown and was later diagnosed with bipolar disorder, also known as manic depression.

Work had brought his illness to the forefront, he said. The manic phase allowed him to work with seemingly limitless energy. Then he would get depressed. He started showing up at work unwashed and unshaven. He would lock the door to his office and never seem to emerge. Finally, he was asked to leave.

At that point, Oberg had no idea what was wrong. "I thought, 'I'm tired; I'm not sleeping well; I'll find a better job.' But I kept getting deeper and deeper into it. I went through whatever money I had. I started getting suicidal."

During that period, he says, he was hospitalized several times. At one point, he wound up living at the Grassroots shelter.

But while surfing the Web one day in 1994, Oberg stumbled onto something called Walkers in Darkness. At the time, the organization was a listserv, a subscriber-based discussion group. "The mere fact of having found a group of people with the same problem did a lot for me," he said.

The Walkers listserv had been founded by David Harmon, a software engineer from New York. In 1996, he turned over responsibility for maintaining it to Oberg, who ultimately turned the list into an elaborate Web site filled with lively chat rooms. From 1996 to 1999, there were 300,000 visitors to the site. Last year, there were 400,000, he said.

"Maybe I was uniquely qualified to do this because I had the illness and the interest and the time on my hands and the knowledge," he said.

Although Oberg sometimes offers advice, he has no training or academic credentials in the field of mental health.

Mostly, he administers and monitors the Web site, among other things ensuring that inappropriate discussions don't take place in the chat rooms.

In 1998, Oberg incorporated Walkers and received a designation from the Internal Revenue Service as a charity. Last year, Walkers received a $25,000 grant from the Gaines Family Foundation in Colorado to upgrade the equipment that supports the Web site.

Following the Sept. 11 attacks, many new people have visited the Web site, according to Oberg, who set up a special chat room to discuss those events.

"Let's try to help them work things out and make them welcome," he wrote to Web site users, who refer to themselves as Walkers. "One does not have to be chronically or even clinically depressed to feel the effects of the Beast."

Today, Oberg, who is retired, spends most of his time running the site.

"All I know is the site is always very busy," he said. "It never slows down."