Leon is 17 years old and has an intense phobia of elevators. When he was 8 years old, he was trapped in a dark, malfunctioning elevator for several hours while a loud emergency siren wailed, causing him severe panic. Now, Leon experiences intense anxiety and starts sweating even if he just hears the chime of an elevator arriving. Yesterday, when visiting a high-rise building for an interview, he saw the elevator doors open, became overwhelmed with panic, and ran to the stairwell to climb fifteen flights of stairs, refusing to take the elevator.