The go-to guy in mental health studies

Ron Kessler develops comprehensive plans to study the underlying reasons for psychiatric disorders among large demographic groups. (Jodi Hilton for the boston globe)

Ron Kessler is a big guy. Big belly, big beard, big laugh, big issues.

He has an offhanded charm about him - T-shirt at work, feet on the table, a bit of salty language - that belies the fact that he is one of the world's leading psychiatric epidemiologists, the go-to guy for the big studies on the big mental health issues of today.

A 61-year-old professor in the department of healthcare policy at Harvard Medical School, Kessler specializes in developing comprehensive plans to study the presence of and underlying reasons for psychiatric disorders among large demographic groups.

He is best known as principal investigator of the National Comorbidity Survey, a widely cited landmark study on national mental health in the United States that is conducted every 10 years (he has led it twice), and the co-director of the World Health Organization's World Mental Health Surveys, a similar project that encompasses 28 countries. Later this week, he will host a symposium in Boston on mental health in the workplace.

How did he get to where he is? Well, that's not so comprehensive a plan. He tells his story with a lot of "I don't know why I did that" and "it seemed like a good idea at the time."

"I started out just following my nose, and the next thing I know I'm in charge of these big things for the federal government and I'm testifying before Congress," he said. Big smile.

He began his career with an interest in juvenile delinquency, drifted briefly to the study of juvenile drug use - a hot topic in the drug culture of the late '60s and '70s - but quickly found he was more interested in the effect that depressed mothers were having on their children's drug use than the children themselves.

As a postdoc at New York University, he took a corporate job on the side, working for NBC on a huge study of the effects of television violence on children, and found that he enjoyed doing statistical analysis of big public opinion surveys, and he found that he liked approaching research from the corporate standpoint because the focus was on finding practical ways to take action.

"There is research to know and research to show," he said. "Very often in academic research we do things that sound scientific and look scientific, but don't mean a whole lot practically. [Corporations] don't do things just for the sake of having it look good."

Kessler describes his work as an attempt "to unpack what it is about a terrible event that makes it terrible."

That could be Michigan in the '80s, looking at what the auto industry recession meant for a family suddenly without work; it could be showing employers how the cost of treating employee depression is far less than what it will cost not to treat; or it could be studying the mental health benefits of getting married - a lot, Kessler says, for the husband; very little for the wife.

"The basic idea in all of this is the distribution of mental health in the population," he said. "How the different things we're exposed to lead to the onset of mental health problems, and how the resources and vulnerabilities of the situation affect their risk."

It is the conjunction of these things that determines why some people develop mental illness, he said, and why, surprisingly, some don't, no matter how dire the situation. Kessler is also a leader in disaster surveillance studies, and has monitored the emotional effects of the Sept. 11 attacks, Hurricane Katrina, and the shootings at Virginia Tech and Columbine High School.

"I know a lot of hardworking people, but I don't know anyone who's able to accomplish as much as Ron," said Paul Cleary, the dean of the school of public health at Yale University. "If you think of a major event that has major psychiatric significance, Ron probably initiated the study or was asked to initiate the study."

Kessler said his current mission is to convince the government to move the national mental health surveys from once a decade to an ongoing basis to better chart the constantly changing character of our mental health.

"Look at all these people who are losing their houses," he said. "We don't have our finger on the pulse of that, but we could. There's a saying in business: 'You can't manage what you can't measure.' That's what we need to do. We need to continually monitor it.

"Nothing's an emergency in an emergency room because you expect it. We have to figure out how to do this from a mental health standpoint."

Hometown: Rancocas, N.J., a Quaker village of 200 people; lives in Newton.

Education: He earned a bachelor's degree from Temple University in 1970, a PhD from New York University in 1975, in sociology.

Family: Wife, Vicki, is a clinical psychologist in private practice; they have four children: Tim, 21, a student at Trinity College in Connecticut; Annie, 20, a student at the University of Wales; Danny, 18, a student at Oberlin College; and Molly, 18, who is finishing high school.

Hobbies: Kessler is an avid squash player and antique collector, and describes himself as an amateur Chinese cook (he went to Chinese cooking school).