Elon Musk said he is “almost always” sober during his late-night — or, in some cases, very early morning — posting sessions on his social media platform, X.

The billionaire Tesla CEO’s comment was made in an interview with journalist Don Lemon, during which Musk discussed his use of the medication ketamine. Musk, who is known for his often erratic behavior, has faced scrutiny following recent reports about his alleged drug use and the potential impact on his companies.

“There are times when I have sort of a … negative chemical state in my brain, like depression I guess, or depression that’s not linked to any negative news, and ketamine is helpful for getting one out of the negative frame of mind,” Musk told Lemon. Musk added that he has a prescription for the drug from “an actual, real doctor” and uses “a small amount once every other week or something like that.”

While Musk said he doesn’t drink and doesn’t “know how to smoke pot,” he didn’t specify whether he was talking about ketamine or another substance when he said he is “almost always” sober while posting late at night.

Musk has previously posted on X about his prescription use of ketamine, a drug used primarily in hospitals as an anesthetic but which is increasingly being explored as a potential treatment for depression, anxiety and other mental health conditions. Musk’s comments offer greater insight into the use of the drug by one of the world’s wealthiest and most powerful people.

Musk denied that he overuses the medication, saying, “if you use too much ketamine, you can’t really get work done. I have a lot of work, I’m typically putting in 16-hour days … so I don’t really have a situation where I can be not mentally acute for an extended period of time.”

Musk said he believes his depression is genetic and added that he doesn’t believe his ketamine use will impact his companies or their government contracts.

“From a standpoint of Wall Street, what matters is execution,” he said. “Are you building value for investors? Tesla is worth about as much as the rest of the car industry combined … so from an investor standpoint, if there is something I’m taking, I should keep taking it.”

The wide-ranging, 90-minute interview between Musk and Lemon — which kicked off a feud between the two men and resulted in the end of a planned deal for X to pay Lemon to post his new streaming show on the platform — covered far more than Musk’s ketamine use, including Musk’s criticisms of diversity, equity and inclusion programs and demand for Tesla’s Cybertruck.

Advertisers on X

Musk also discussed the state of the core advertising business on X, which has suffered since the billionaire acquired the company formerly known as Twitter because of a rise in hateful and controversial content on the platform. Musk previously said advertisers who left X over concerns about antisemitic content could “go f**k yourself” and accused them of killing the company.

In the interview with Lemon, Musk said that almost all of the company’s advertisers have returned, and “it’s a very short list of advertisers who are not coming back to the platform, and our advertising revenue is rising rapidly and our subscription revenue is rising rapidly and I feel very optimistic about the future of the X platform.” Still, the billionaire appeared uninterested in adjusting X’s policies to appease advertisers who have left the site.

“You can choose where you want your advertising, what you want your advertiser to appear next to, but you can’t insist on censorship of the entire platform,” he said. “If you insist on censorship of the entire platform, even where your advertising doesn’t appear, then obviously we will not want them as an advertiser.”