TEHRAN — Less than a year ago, he was running a thriving computer accessories business, driving a new car and renting a comfortable two-bedroom apartment in the center of Tehran. But last month, Kaveh Taymouri found himself riding a rusty motorcycle on his hourlong commute to his family’s new lodgings, a 485-square-foot apartment in one of the city’s worst neighborhoods, next to its sprawling cemetery.

When he arrived home one recent night at 10:30 from his new job at an arcade, there was no food on the stove. The sandwich he had for lunch would have to do.

Nevertheless, his wife and former business partner, Reihaneh, said she thought his mood was improving.

“At least he has stopped screaming in his sleep,” she said.

Before their “downfall,” as they call it, the Taymouris were the model middle-class Iranian family, prosperous college-educated business owners who made enough money to save for a down payment on their own home. Now, they are a model for a different sort: the millions of middle-class Iranians who almost overnight have seen their lives shrink, dragged down by economic forces beyond their control.