When Lt. Cmdr. Scott L. Johnston, PhD, began his psychology training nearly two decades ago, he never dreamed of a 10-year career as a Navy psychologist that would lead him to the White House. But today, he serves as the presidential support psychologist in charge of ensuring the psychological health of those who protect the nation's top leaders.

"Now I'm working for the president, flying in his helicopters and entertaining his guests at the White House," says Johnston, who first joined the Navy in 1993 to do a predoctoral internship at Balboa Naval Medical Center in San Diego, Calif.

Johnston, who is embedded with the Marines and wears the uniform, spends most of his time maintaining the well-being of the troops who protect the president. The Marines he works with are stationed at Camp David, the White House or in Quantico, Va., with the presidential helicopter squadron.

Since the troops must hold a very high presidential clearance in order to carry a loaded weapon around the president, they might be apprehensive about disclosing any emotional struggles--such as stress, marital problems or job adjustment issues--for fear of losing their clearance, Johnston says.

"Having me there allows them to get to know me as one of the guys, and it makes them a lot more comfortable to deal with issues before they become a problem," he explains.

Johnston also does psychological evaluations using personality tests, questionnaires and interviews to assess the Marines applying for special duty to protect the president. While he can't be too specific on what mental health characteristics he looks for because of security issues, he says he screens out candidates who, for example, are depressed or have anxiety disorders.

And because of his top security clearance, Johnston is also able to provide psychological services to some staffers at the White House--what he considers coaching to enhance their work performance or handle work-related conflicts. Johnston also serves as a White House social aide and acts as a ceremonial escort to the guests of the president and first lady at state dinners, award ceremonies and other special events.

He's a man of many jobs, and he says the military has allowed him an exciting opportunity to use psychology all over the world--literally. For example, he spent six months in 1999 on the Navy aircraft carrier the USS Constellation, where he was in charge of providing mental health services for 10,000 men and women as they traveled around the globe.

"The military--in all its ranks and positions--gives you a lot of responsibility really quickly," Johnston says. "I've appreciated that. It's pretty scary initially, but ultimately, it can be really exciting and rewarding."