When meditation goes wrong

Although it has been claimed that meditation does help in several ways, I have read on the Internet that there are cases where psychotic episodes, schizophrenia and suicide tendencies arise after meditation retreats. Where I have read that this has happened is in Goenka's Vipassana retreats, which are 10 days long retreats. In particular, the only way to start at Goenka's retreats is first with a 10 days retreat. I did one of those retreats without any unhealthy consequences, but I do confess that during the retreat I was kind of 'watching' myself to avoid any unhealthy episode. - Is there any explanation to this unhealthy responses to meditation retreats? - Is it clear why this happens? - Is there any way to minimize chances to get that wrong ? In articles of Vipassana Research Institute it is kind of stated that the main source of this problems is that meditators have tried 'other traditions'. Is this a credible **scientific** answer? Some references I found on the web: - Mental Health and Intensive Meditation Retreats - Meditation-Induced Psychosis - For Whom May Participation in Mindfulness-Based Stress Reduction Program be Contraindicated? - Psychiatric Complications of Meditation Practice - Terrible and Traumatic Experience at Goenka Retreat This one is quite an informal blog. I have found that it is frequently cited. - The Potential Downside To Vipassana . Again, an informal blog.