Jett died at the age of 16 in January 2009 from a seizure during a family holiday in the Bahamas, reported BBC online.
"The truth is, I didn't know if I was going to make it. Life was no longer interesting to me, so it took a lot to get me better," he said.
Both his father and his mother Kelly Preston have since confirmed their eldest son was autistic and had a history of seizures.
The couple have two other children: 13-year-old daughter Ella Bleu and three-year-old son Benjamin.
"I will forever be grateful to Scientology for supporting me for two years solid, I mean Monday through Sunday. They didn't take a day off, working through different angles of the techniques to get through grief and loss, and to make me feel that finally I could get through a day.