About 150,000 Maryland adults — or 1 in 30 — have a gambling problem, a state-mandated study by the University of Maryland Baltimore County found.

The study by the university’s Institute for Policy Analysis and Research predicted that the numbers would likely rise in the near term.

Intended as a base-line study to help assess how the introduction of slot machines in the state will affect gambling addiction, the report said that although nearly 90 percent of Marylanders have gambled on something, from football games to bingo, in their lifetimes, only 3.5 percent could be classified as problem or pathological gamblers.

“It is a major part of the population, but it’s within the national range,” said Judith Shinogle, the study’s team leader. “If you think about Maryland’s proximity to New Jersey and New York City, this is not out of range.”

The rate trails only California and Nevada among the nine states that have been surveyed on this issue.

The study sampled 5,987 households by telephone between Sept. 7 and Oct. 31, 2010.

Those most at risk for developing gambling addictions are single men between the ages of 18 and 29, either African American or Hispanic, with less education and income than the general population, the study found.

Maryland’s first slot machine casino opened in September, joining legal betting on horse racing and lotteries. An effort to legalize table games, such as blackjack and roulette, is expected later this year.

“While the prevalence of problem gambling tends to rise when access to gambling increases, research suggests it will eventually level out, even when gambling accessibility continues to increase,” the report concluded. “However, rates may rise three- or four-fold before this occurs, and even then, active measures may be required to achieve stabilization.”

Most gamblers in Maryland play casino games or the lottery, but the small percentage who gamble on the Internet spends the most money — $553 per month, on average. Those who play at casinos on a regular basis spend about $214 per month. Marylanders who gamble at all average $189, “but as frequency of gambling increases, so does the amount spent,” the report said.