Tech pioneer Elon Musk has admitted that stress is taking a heavy toll on him personally in what he called an “excruciating” year.

The New York Times said the chief executive of electric car maker Tesla alternated between laughter and tears during an interview in which he said he is working up to 120 hours a week and sometimes takes the sedative Ambien to get to sleep.

But he denied being “on weed” when he posted news of a potential 72 billion dollar (£57 billion) buyout of the publicly held company, according to the newspaper.

“This past year has been the most difficult and painful year of my career,” he said. “It was excruciating.”

The interview offered rare insights into Mr Musk’s personal life and thinking. He stood by his tweet last week saying he might take Tesla private and that he had secured the funding to do so.

Asked if he regretted it, he said: “Why would I?”

Musk has a reputation for being an eccentric visionary, but his out-of-the-blue announcement of a potential buyout raised a huge ruckus and pushed Tesla’s shares up 11% in a day, raising the company’s value by 6 billion dollars (£4.7 billion).

The shares later eased back, and then plunged by 6% in early trading on Friday.

The Wall Street Journal reported that government regulators have subpoenaed Tesla as they dig deeper into his disclosure of the potential buyout.

That signals regulators are investigating if Mr Musk was truthful in the tweet about having the financing set for a deal that analysts have estimated would require 25 billion to 50 billion dollars (£20 billion to £40 billion).

He said in the interview that he had wanted to offer a roughly 20% premium over where the stock had been trading, which would have been about 419 dollars. He decided to round up to 420 dollars — a number that is code for marijuana in counterculture lore.

“It seemed like better karma at 420 dollars than at 419 dollars,” he said in the interview. “But I was not on weed, to be clear. Weed is not helpful for productivity. There’s a reason for the word ‘stoned’. You just sit there like a stone on weed.”

The New York Times said that in response to questions for its article on the interview, Tesla issued a statement from its board, excluding Mr Musk, that said: “We would like to make it clear that Elon’s commitment and dedication to Tesla is obvious.”

In the interview, he said he fired off the tweet while on his way to an airport, and his reference to having secured funding referred to a potential investment by Saudi Arabia’s government fund.

Mr Musk, 47, said sometimes he did not leave the Tesla factory for three or four days straight, and that he had not taken off more than a week at a time since he was sick with malaria in 2001.

His social media antics have raised eyebrows as he berated analysts and falsely accused a cave diver of being a paedophile after the man was sceptical about a mini-submarine Mr Musk sent to possibly help rescue young football players from a flooded cave in Thailand. He later apologised for that remark.

The report cited sources as saying Tesla has been trying to find another senior executive to help relieve some of the pressure on Mr Musk.

He said he did not intend to give up his roles as chairman and CEO but that if there was someone who could do the job better, “they can have the reins right now”.

In a separate report, the Wall Street Journal said securities regulators have been investigating if Tesla misled investors about production problems for its Model 3 car.

The company could face sanctions if regulators find it misled investors about production delays.