These attacks deeply constrained both their lives. Recently, Peter Van Sant spent time with Murphy and Dyer as they tried to overcome their problems. He even followed Murphy step by step as she tried a new treatment to rid herself of panic, as 48 Hours first reported in February.
"It's depressing," explained Murphy, in her 20s, who lives in Randolph, Mass. "You can't hold a job, can't go to school, can't do anything. There's been months when I haven't left the house."
The attacks can occur at any time, for no apparent reason. For many, the attacks are so severe that people believe they're going to die.
"My legs get shaky," Murphy said. "I can't control my own body. Everything gets blurry. But when it actually blacks out, and you can't see anything, that's probably the scariest thing." These episodes can last for a few minutes or days, Murphy said.
Sometimes Murphy even panicked at home. She didn't like to be alone, she said.
"(Panic attacks) are a fight/flight response occurring at the wrong time," said Dr. David Barlow, director of the Boston University's Center for Anxiety and Related Disorders. "It's almost like you'd been hit by lightning before, and knew you were going to be hit again, but never knew where or when."
Panic disorder strikes twice as many women as men. This was no consolation for Dyer, however.
"It's the scariest thing I've ever felt before," he said of his attacks. At 6 feet 4 inches and 215 pounds, the car salesman in Annapolis, Md., also in his 20s, doesn't seem like the panicky type.
Dyer was also confined by his fears. He dreamed of becoming a professional soccer player. But in high school he actually turned down a shot at a college scholarship.
"I didn't play soccer in college because panic had become such an issue at that time," Dyer said. "I (was) having panic attacks driving 20, 30 minutes away from the house. How (was) I going to go six hours away and play college?"
Over the years, the attacks, which started in hi midteens, became more intense. "I could have full-blown panic attacks more than once a day," he said.
His fear put a crimp in his marriage, too. Several times his wife Jessica went on vacations without him because he was too afraid to travel.
In some cases, Dyer could barely get to the airport. "When we were getting close, my body would physically start to shake," he said. Once Dyer's entire extended family went on a Christmas cruise without him.
"You just feel like a complete and total failure," he said.
For her part, Murphy, who has suffered from panic for about eight years, only felt comfortable on a one-mile stretch of road outside her house. She didn't have a full-time job and instead helped out in a pet store. If she began to panic, she could simply go home, she says.
Both Murphy and Dyer tried antidepressants, which can help many patients with panic disorder. The drugs did not work for either of them.
Recently Dyer tried a new treatment. At Boston University's Center For Anxiety and Related Disorders, he underwent a week of intensive therapy designed to teach him how to overcome panic.
He says it worked. Before the therapy, he couldn't drive over long bridges. Now, though, he can drive over bridges with ease. Dyer decided he wanted to try something even scarier, so 48 Hours flew him and his wife to Florida so that Chad could fulfill his dream of going skydiving. With the cameras rolling, the couple made the jump. Afterward, Dyer was thrilled.
Murphy decided to try the same treatment. Over the first few days, Murphy learned how panic attacks work: The body's fight or flight mechanism kicks in at the wrong time.
Kami White, the psychologist working with Murphy, had her hyperventilate to simulate an attack. She tried to get Murphy to realize that an attack does not mean she is about to die.
On the fourth day, White and Murphy took the "T," as the Boston subway system is called. Murphy had never ridden on it before. Murphy said she was tense, but "You know it's not going to kill you."
On the fifth day, White and Murphy went for a drive. In the middle of the trip, White had a surprise task for Murphy: She was to drive, by herself, to a nearby town, where she would meet White. Because Murphy was unfamiliar with the area, she had to use maps to navigate.
Murphy was surprised and very scared. She began to curse at White. But she agreed to try.
For the next 30 minutes, Murphy was forced to confront her panic alone. She was scared, but stayed focused. When she reached her goal, she was ecstatic.
"That is a huge turning point for Theresa," White said. "She just wanted to be able to go with her friends somewhere in the car and be able to get there and back without a panic attack."
"Now that I know most likely nothing's going to happen; it just takes away the panic of it," Murphy said.
A few weeks after the treatment, Murphy said that she is a happier person. The woman who could barely leave her house three weeks earlier got her first job.