A clinical diagnosis of Washington sports fans, circa April 2011, requires neither a couch nor a medical degree, though a box of tissues might come in handy. Instead, kindly stroll the Verizon Center concourse on a lovely Wednesday evening, with the Washington Capitals and New York Rangers set to begin overtime, tied at one goal apiece, in the first game of a best-of-seven National Hockey League playoff series.

“Heart attack,” said Josh Shaffer of Linden.

“Like I just got off the Rebel Yell at Kings Dominion,” Tom Coleman offered.

“I need a diaper,” said Chris Donovan of Reston.

“It feels like you’re walking up to the altar,” said Jim Gorlinsky of Fairfax. “And you’re not sure if the Caps are gonna say yes or not.”

Washington won the game 18 minutes 24 seconds into overtime, and nerves were temporarily calmed — middle-aged men in dress clothes whooping, co-workers exchanging sweaty hugs, Cahlan Mazur seizing his mom’s walker and thrusting it into the air again and again. But, as Capitals fans know, it takes four victories to win a playoff series — and Game 2 against New York is Friday night.

To be sure, sudden-death postseason hockey might cause such a malady — “Playoffitis,” Coleman called it — in many cities, among fans of many NHL teams. The symptoms seem especially acute in Washington, however, where sports fans have been battered into a state of near-constant skittishness.

For one thing, the city’s other pro teams have been mired in better than a decade of frustration and disappointment. The Redskins have won a single playoff game in the past 10 years. The Wizards have won a single playoff series since 1982. The Nationals have never had a winning season. D.C. United, which did last win the Major League Soccer title in 2004, hasn’t made the playoffs in three years.

But more than that, these Capitals have toyed with their fans’ emotions since becoming playoff regulars in 2008. They’ve had home-ice advantage in all four of their playoff series. All four have gone to a deciding Game 7, in the District. And the Capitals have lost three of those games, including last year’s shocking upset to the Montreal Canadiens after the Caps had amassed the NHL’s best regular season record and taken a series lead of three games to one.

“Once bitten, twice shy,” the team’s television play-by-play announcer, Joe Beninati, said on Thursday. “I understand where the people are coming from, and yeah, you can feel it in the stands: As soon as the game is nothing-nothing in the third period, fans are like, ‘Oh God, when is it going to happen? . . . It’s gonna happen to us again.’ I wish that specter would go away. I want it to, and it will. They’ve just got to win.”

And there’s no shortage of sentiment that this might be the year. Despite a turbulent season filled with injuries and losing streaks, the Caps again finished with the Eastern Conference’s best record, giving them the top seed in the first round of the playoffs against the eighth-seeded Rangers. They adopted a more defensive playing style, which has typically been the mark of Stanley Cup champions. They made several late-season trades, bringing in steady veterans such as Jason Arnott, who assisted on Wednesday’s game-winning goal. National analysts labeled them the best team in the East, and oddsmakers installed them as Eastern Conference favorites.

But the tension remains among fans who seem torn between cautious optimism and existential despair. It was still there in a Chinatown bar, an hour after the Caps claimed Game 1.

“We’ve been down this road; we know,” longtime fan John Weaver said. “If I wouldn’t have had the presence of mind to buy an overtime beer, I don’t know what I’d have done.”

That anxiety was pinging around the Internet, where fans have spent days sharing their stories of stress and worry.

“Terrified,” tweeted Danny Rouhier, a comic and host on sports-talk station 106.7 The Fan. “I have the DC Sports Fear.”

“I need to calm down a bit. My swearing is scaring the dog,” tweeted Natasha Jasso, a mother of four from Stafford.

And it was still on display Thursday, when fans attempted to steel themselves for yet another tangle with dread in Friday’s Game 2 at Verizon Center.

“Last night was rough,” Lizzie McManus said while watching the Caps practice at their training facility in Arlington.

“Really rough,” her friend Ella Gomez agreed.

“I almost drove my car off the road,” Alana Gillen said inside the team’s pro shop. “So much rides on this. D.C. needs it. The Caps need it. D.C. doesn’t have a winning team, and it’s something for us to be proud of, especially after last year.”

The players are largely shielded from such expectations. They’re not trying to redeem a generation of Washington sports teams, nor are they responsible for the Caps’ playoff disasters of the 1980s and ’90s. And yet the region’s tension is palpable for those who are paying attention.

“It’s hard to not notice how badly they want us to win, how badly they want to celebrate,” defenseman Karl Alzner said. “They really want us to win, but at the same time they’re nervous because they know what happened last year. I can understand that.”

If nothing else, fans seem to have built up a fellowship in shared stress, a nightly group therapy session that extends from blogs to talk-radio stations to the arena itself. When Capitals star forward Alex Ovechkin tied Wednesday’s game late in the third period, two fans sitting behind the net headbutted each other. When fellow Russian Alexander Semin won it in overtime, Art Litvak jumped into the arms of a man whose name he couldn’t recall — “Dude, I don’t know, I was just exuberant,” he tried to explain.

And after the game, fans were still grappling with their emotions.

“Hope every game isn’t like this. 1 vs. 8 series shouldn’t be this nerve-wracking,” one fan messaged ESPN host and Washington native Bram Weinstein.

“Welcome to DC,” Weinstein replied.