By Mike Brunker, msnbc.com writer and editor

The vast oil spill in the Gulf of Mexico has been more traumatic than Hurricane Katrina for coastal residents, with 30 percent of those interviewed apparently suffering mild to serious psychological distress, according to a survey by a health care provider released Thursday.

The survey of 406 Gulf Coast residents, conducted for the nonprofit Ochsner Health System, found that the mental health impacts from the BP’s Deepwater Horizon spill were greatest for residents of Louisiana, the young and the poor.

Eighteen percent of Louisiana residents were suffering “probable serious” or “probable mild-moderate” mental illness based on the K6 psychological distress scale – more than double the rate found in a similar survey conducted in July 2007, two years after Hurricanes Katrina and Rita hit the state, the survey found. Fourteen percent of Floridians, 12 percent of Mississippians and 10 percent of Alabamans were similarly afflicted, it said.

Hardest hit were residents earning less than $25,000 annually, 32 percent of whom appeared to have “probable serious” mental illness on the K6 scale, it said.

Young respondents (22 to 44 years old) were in the same category, with money and work being the two biggest causes of their stress.

You can read more about the survey by clicking here.

Msnbc.com's JoNel Aleccia reports from New Orleans:

Volunteers flocking to the Gulf of Mexico to help clean up tainted seas and shoreline — including some 17,000 members of the National Guard — may be among those at highest risk for potential health problems, scientists said today.

That's because ad-hoc workers may not have consistent training or monitoring to limit front-line exposure to chemicals, heat, accidents, stress — even wildlife — that could pose a threat, said experts gathered for a meeting on oil spill health effects.

"Some of these guys have never been in a swamp, and they don't recognize there are poisonous snakes there. You don't want them coming back later as another injured party," said Paul J. Lioy, an expert on 9/11 toxic exposures and a professor in the Department of Environmental and Occupational Medicine at the University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School in Piscataway, N.J.

Lioy and others urged better monitoring of all those associated with the spill clean-up, including more than 25,000 volunteers who have signed up so far, according to the Deepwater Horizon joint operations center.

Last week, President Barack Obama promised the services of the National Guard. Before that, images of oil-soaked birds and shorelines spurred thousands of people to reach out to dozens of wildlife groups and other agencies arranging crews to help. Most have been kept away from the heavy lifting of clean-up, but some could be exposed to fumes, tar and other contaminants that have caused mild symptoms among some workers. In addition, they could face other hazards affecting workers and community members, said Dr. Howard Osofsky, chairman of the Department of Psychiatry at the Louisiana State University Health Sciences Center in New Orleans.

Osofsky, who has studied mental health effects of hurricanes and other disasters, said he expects "good-hearted" volunteers to show up with difficult side effects.

"We'll see heat exhaustion, we'll see medical problems, we'll see psychological stress," he said, including the stress of helping people who had barely begun to recover from Hurricane Katrina.