Wall Street Journal reporter Evan Gershkovich remains "defiant" six months after he was detained in Russia on spying charges, which he and the Journal strenuously deny, his mother told CNN's Anderson Cooper Thursday night.

"He's smiling. He understands what's going on," Ella Milman said. "And I have to say, under all the circumstances, he's doing really well."

Gershkovich's parents have been able to go to Russia twice. They saw him in June and were able to talk to him, though Cooper noted he was essentially in a glass box.

"Being there, it was like having him back," his father, Mikhail Gershkovich, said. "Just the physical presence and his voice made you very happy."

Gershkovich was arrested in March during a reporting trip. The FSB, Russia's main security service, accused him of trying to obtain state secrets — a charge Gershkovich and his employer have extensively denied.

If convicted, he faces up to 20 years in prison.

Gershkovich's parents left the Soviet Union to come to the United States. Evan's initial reporting trips in the country didn't worry the two of them.

"He came to Russia in 2017. Things were a lot different at the time," Milman said.

The family keeps in touch with Gershkovich through letters, which are up to 10 pages long and include printed pictures. His sister, Danielle Gershkovich, says they can hear his voice through his writing — fitting, Cooper noted, as he's a print journalist.

"It's like sitting on the couch," Milman said. "The only thing is that the answer comes the following week."

Those who want to help need to keep the focus on Evan, Danielle said, whether it's people posting on social media or reading his reporting.

From a young age, Gershkovich was curious and easily connected with people, Milman said.

"He always would come home after his fancy trips and wanted to have a hamburger and buffalo wings and watch baseball and watch American football," Milman said. "He's an American boy who has roots in Russian culture."

The journalist's detention is a source of tension between Washington and Moscow.

"The US position remains unwavering. The charges against Evan are baseless. The Russian government locked Evan up for simply doing his job. Journalism is not a crime," US ambassador to Russia Lynne Tracy said to reporters earlier this month.

In September, a Moscow court refused to hear an appeal against his pre-trial detention, leaving Gershkovich behind bars. His pre-trial detention has been extended twice since his arrest, once in May and again in August. An appeal against his first pre-trial detention was also denied.