There have been two major scientific studies done on the visonaries since the apparitions began in Medjugorje on June 25, 1981 by the best scientists in the world. The most recent of which was in 1998. Both drew the same conclusions,
which are that the visionaries are healthy mentally and physically, they are not hallucinating, are not lying, and are definitely experiencing something that is beyond our scientific understanding that is unexplainable.
It is also interesting to note that during the experiments, one of the things being monitored was brain activity. Most of us are able to use around 15% of our brain during normal activities. It is facinating to note that at the moment when Our Lady appears, the visionaries brain activity jumps to 100% and stays at this level until Our Lady leaves.
As a personal testimony, having visited Medjugorje almost 80 times over the last 11 years, and personally knowing most of the visionaries, I can say that in my opinion, and without any doubt, the apparitions are authentic. I also want to shift the focus to the "Fruits of Medjugorje". As scripture says: "You will know them by their fruits". There are thousands of documented physical healings and literally countless spiritual healings and conversions that have taken place in Medjugorje over the last 25 years. Please refer to the following documents for the published results of the studies done on the visionaries.