"The New Wine" (1954), a short story by John Christopher. It has appeared in a number of anthologies and collections; any of these covers look familiar?
At the beginning of the story, the first interstellar expedition is about to leave for Procyon:
"That time factor," she said, "is it certain? I don't understand mathematics; to me it seems fantastic."
"I could go over the theory with you, but it would be wasting the little time we have. It's certain enough. The ratio, as far as this trip is concerned, is approximately twelve to one. For us, eight years—for the world we leave behind, a century. we return in late April in the year 2129. That's the nearest our predictions will take us."
Meanwhile, some mad embryologists are planning to make all newborn babies telepathic:
"But to do a thing like that, after only three experiments! And without any reference to the wishes of the people concerned. Aren't you afraid of it going wrong?"
"Have you considered the alternative to a simultaneous planetwide irradiation like the one we are doing? The principle has been discovered; you can't turn science backwards. The choice is between doing what we plan to do or having the advance take place piecemeal. If we did that, there would be trouble. Resentment of those family with ordinary children against those with telepaths. National resentments, leading perhaps to wars. All the confusion of an interregnum between the old and the new. we shall avoid all of that. The world will go forward in one giant's stride."
Needless to say, it goes horribly wrong. The astronauts come back to a dying world:
"Some of them grew up. Not many. They were all right as children—except the highly-strung ones, of course. But when they got to being ten or eleven and over it got them like flies. Maybe one in a hundred got out of the teens. I had a couple of kids myself; folks were always hoping that the effect would die away, though the scientists said it wouldn't, right from the start. My boy got to fifteen."
"But why did they die?" Rennis asked him. "What killed them? Was there something else as well as telepathy?"
He looked puzzled. "Why, no. The telepathy killed them, of course." To him, clearly, it was something self-evident. "Bound to. Some of them shot themselves or hanged themselves or whatever, but most of them just died."
"But why?" Harl said. "Why?"
"Because people have got bad minds. Why else? I guess you all know what you are like if you look at yourselves deep down and honest. Liars, cheats, murderers. I guess we're all like that—always have been. What comes out of our mouths has been . . . through a filter, I guess you might say. But there were no filters for the telepaths. It hit them and kept on hitting them all the time. The better any one of them was, the quicker it killed him—or her, but the girls lived longer, as a rule."
Awkright said listlessly: "So that's how it was."
Rennis said: "But was it a fixed mutation? Might there not be isolated outposts of the telepaths—and their children?"
"Their children?" The old man laughed. "The ones who grew up enough never married. You ever try falling in love with yourself?"
The old man was pinning his hopes on the female astronauts:
The old man said: "That's why I wanted to live to see you come back. So that things could start again."
They looked at him.
"They called me Lee after the captain," he said. "I knew all about the flight. I saw the records. That you had two women in the crew. Things can start again now."
Rennis and Awkright turned and began to walk away.
"Yes," Harl said. "Two. Sub-Navigator Mary Rogers. Assistant Medic Lucy Parino. Aged, respectively, fifty-two and fifty-four."
