They call it the end-of-the-line syndrome: Residents choose to live on Martha’s Vineyard for its solitude but then turn to drugs and alcohol during the long winter months. Now, some mental health advocates fear a casino could worsen these problems, particularly in the offseason when the population dwindles to 15,000 and the island becomes more isolated.

“From the point of view of my patients, a casino on Martha’s Vineyard is a disaster,” said Dr. Charles Silberstein, a psychiatrist at Martha’s Vineyard Hospital, who treats residents with drug and alcohol addiction. “Like some alcoholics at a family gathering, it triggers them.”

The Wampanoag Tribe of Aquinnah, which says it wants to operate a casino year-round on the western end of the island, emphatically rejects those predictions. The tribe says a casino will draw winter tourists and provide jobs and entertainment for residents, improving livelihoods and helping people avoid drugs and alcohol during the lonely winter season.

“I’ve been involved with tribal gaming for 25 years and I’ve heard that argument virtually every time, and virtually every time it turns out the opposite is the case,” said Scott Crowell, a lawyer for the tribe, referring to warnings that casinos breed substance abuse. “If you have a struggling community that has vices and then provide them with steady jobs and steady incomes in the local area, the water lifts all boats.”

Thirty-one percent of Vineyard residents have reported excessive alcohol consumption, compared with 16 percent of residents nationwide. About 14 percent say they suffer from depression, compared with 6 to 10 percent of residents nationally, according to a 2006 report on island health conditions, which Silberstein coauthored.

Crowell said he expects most of the casino’s revenue would be generated during the summer, when wealthy visitors from New York and Washington flock to the Vineyard and the island’s population swells to 115,000. However, he said, the tribe plans to keep the casino operating during the offseason as well, if the market will support it.

He argued that the casino would serve as a magnet for winter tourism and that it could even draw enough visitors to support an additional ferry terminal near Aquinnah, the town famous for its russet cliffs and historic lighthouse, where the casino would be located. Currently, offseason visitors have to take a 45-minute ferry ride from Woods Hole to Vineyard Haven and then drive for at least 30 minutes to reach Aquinnah.

“It’s not an easy trek,” said state Representative Timothy R. Madden, a Nantucket Democrat whose district includes the Vineyard. “I don’t see it having the draw or accessibility that would be needed to make it a worthwhile venture for them.”

Clyde W. Barrow, a gambling specialist at the University of Massachusetts Dartmouth, said most gamblers would prefer to drive to Foxwoods in Connecticut rather than make the long trip to Aquinnah, where the casino’s license will limit its offerings to video lottery terminals, poker, and bingo-type games.

“Theoretically, it could be viable, but that means that for probably eight months of the year, it’s going to draw primarily local residents,” Barrow said. “And my guess is Vineyard residents aren’t big gamblers. People don’t go live on Martha’s Vineyard to search for neon lights.”

Lia Nower, director of the Center for Gambling Studies at Rutgers University in New Jersey, said, however, that on an island with few winter entertainment options, a casino would be a major attraction for residents, some of whom will become hooked on gambling.

“It does create a more dangerous environment when you have fewer people in an isolated area,” Nower said. “It’s a formula for lots of problems for a portion of people who live there year-round.”

Mark Jenkins, president of the board of Vineyard House, which provides housing for residents recovering from drug and alcohol addiction, said the stresses of the seasonal economy, as well as isolation in wintertime, are often blamed for the island’s substance abuse problems.

“In the offseason, it’s such a small community, to get away from your triggers, or your demons, you don’t have the option of saying, ‘I’m going to move 35 miles away, and start a new life,’ ” Jenkins said.

The tribe is likely to face legal challenges before it can build a casino.

Officials from the state of Massachusetts and the town of Aquinnah say the tribe forfeited its federal gambling rights in the 1980s, when it agreed to abide by state law on its sovereign territory as part of a land settlement. But the tribe cites a federal opinion issued last month that says it did not give up its gambling rights under that settlement.

If the tribe can build a casino, some economists believe it could increase wages and cut unemployment. The Vineyard has a 4 percent unemployment rate, compared with 7.2 percent statewide. Median household incomes on the island are slightly higher than the state average, although the number of residents living in poverty has been rising.

“Based on the research I’ve done and I've seen, I would say, generally, there’s a net positive,” said Doug Walker, an economist who studies gambling at the College of Charleston in South Carolina. In addition, he said, “it represents another form of entertainment that people might enjoy.”