The number of patients researching prescription drugs online has doubled since 2005 to 102 million, according to Manhattan Research data.

The firm’s Cybercitizen Health study estimates that around 157 million consumers will have looked for any health information online in 2009. Manhattan Research said the main theme of this year’s study was the increasing diversity of the patient media mix, indicating that advertisers can no longer reach a particular audience effectively through any one media outlet.

“The online health experience for the typical consumer is rapidly evolving from a defined session searching medical reference materials to a more comprehensive experience that may include reviewing ratings for a specific drug, posting a comment online about a specific treatment option or submitting an information request through a pharmaceutical company site,” said Manhattan Research president Mark Bard. “The transition over the past five years is about so much more than just the population increasing in size – they have also increased their expectations with regard to the online experience specific to health and pharmaceutical information and services online.”

Bard added that mobile devices are coming up fast.

“While mobile access remains an advanced market of users in 2009, and even more so specific to health information on the mobile device, it has the potential to increase very fast in the coming 12 to 24 months as consumers replace their existing phones with phones including data capabilities and online access,” said Bard.

Manhattan Research conducted online and phone interviews of 8,600 US adults in the third quarter of 2009 for the study.