But Bild newspaper reported several foreign intelligence services are unconvinced and are trying to get their hands on her medical files.
Merkel flew to Japan a few hours after the latest attack and appeared unaffected at the G20 summit.
But, despite smiles for the cameras, she seemed a less dominant figure than at previous summits. Speaking of the attacks, she said she was convinced that "this reaction will disappear just as it has arisen".
Asked what lay behind it and if she had seen a doctor, she said she had "nothing in particular to report".
She gave way to other EU leaders led by France's Emmanuel Macron and dropped her support for the German Manfred Weber to become the next head of the European Commission.
For once, she seemed peripheral to the main business as Donald Trump and China's President Xi Jinping agreed to break the standoff between their countries and restart trade talks.
Trump backed away from earlier threats of imposing new trade sanctions on China.
"I think we can help each other, if China would open up, you're opening up the largest market in the world," he said.
"Right now China isn't open to the US. That shouldn't have been allowed to happen."
Not for the first time, Trump ignored the niceties of diplomacy when he offered North Korean leader Kim Jong-un a meeting via Twitter.
"I will be leaving Japan for South Korea," he tweeted. "While there, if Chairman Kim... sees this, I would meet him at the Border/DMZ just to shake his hand and say Hello(?)!"
He later claimed his offer to meet at the demilitarised zone (DMZ) at the border between the two Koreas was a spontaneous idea.
But The Hill, a Washington news website, claimed he told it of his plans on Monday, asking for them to be kept quiet for security reasons.
Yesterday, the US president also praised Mohammed bin Salman, the crown prince of Saudi Arabia, even as Theresa May and other leaders pressured the prince over the killing of journalist Jamal Khashoggi.
