You're right to mention the conflicting nature of much of the data available. I quite agree that there is noteworthy evidence both for and against the IBS link,

You're right to mention the conflicting nature of much of the data available. I quite agree that there is noteworthy evidence both for and against the IBS link, but the fact that IBS lawsuits led Roche to pull the drug off the market in 2009 suggests that there must be some compelling evidence of a link. It's anecdotally accepted that isotretinoin users have a tendency to avoid reporting depression so as to continue being prescribed the drug. It's common sense – of course there will be underreporting in cases where the reporting will prevent someone being prescribed a drug they wish to take.