Doughty was found dead in the gym at his home in Skillington, a village in the central-eastern county of Lincolnshire on Saturday.
Police told an inquest in Lincoln on Wednesday that they believe the 54-year-old Doughty died of natural causes. He was described by his family as fit and well when he said he was going to work out in the gym.
Doughty bought Forest for £11 million in 1999, when the team was in the second tier, but couldn't bring success back to a club that won the European Cup in 1979 and 1980.
Forest haven't been in the Premier League since being relegated in 1999.