Doctors often understate the seriousness of illnesses, and many withhold information from patients, according to a survey published last week by Health Affairs.

The survey was conducted in 2009 and included 1,891 practicing doctors nationwide. More than half of respondents indicated that they sometimes provided patients with an overly optimistic view of possible outcomes for illnesses.

Additionally, about one-third of respondents said they did not believe it was necessary to disclose serious medical errors to patients, and one-fifth said that in some circumstances it was OK to tell a patient something that was untrue.

However, the vast majority of physicians agreed that they should fully inform patients about the risks and benefits of treatments and should never improperly disclose confidential information.