Whereas most suicides before the revolution were for reasons of mental health, those since have been driven largely by economic hardship and a desire to challenge the authorities. They are often carried out in front of administration buildings.

Mr. Dridi had previously tried to burn himself in public in 2012, but was stopped by onlookers.

He said he had earned about $400 a month before the revolution, which is twice the minimum wage in Tunisia. Now, he said, he never knows how much he will sell, or how many times the police will harass him.

Cases like his are a sign of social despair and resentment toward officialdom, medical personnel say.

“Most of those who survived told us they just could not take it anymore,” said Nadia Ben Slama, a psychologist at the Ben Arous hospital. “They frequently used two words in Arabic: el kahra, which means helplessness or the feeling of being oppressed, and the word hogra, which means scorn or contempt from others.”

“There is a symbolism in the public gesture of self-immolation,” she added. “It is usually to denounce injustice or an oppressor, but also to make the other one feel guilty, the one who witnessed the injustice and who did not act on it. That one is society in general.”

Sometimes self-immolation is threatened to force the hand of the authorities. That is what Imed Ghanmi, 43, an unemployed teacher, did when the police confiscated smuggled merchandise he was selling on the street to support his family.