This is one of those threads that pops up every few months...someone requesting links that will give scientific validation to OMT. Well...there is quite a bit of OMT research going on. It's been done for years, but it is difficult to design credible studies sometimes just like in other modalities. For instance, you CAN'T design a double-blind study comparing a surgical and pharmacological solution to the same problem. Everyone knows who got what treatment. OMT is similar in that way. A lot of studies have tried OMT vs sham techniques, but you still run into multiple problems there as well.
Another point...when some type of treatment other than OMT fails you don't go running to the patient with literature and say, "look here, this is safe and it works", so why would you do that with OMT? In any treatment plan you discuss the details and risks with a patient before you begin and you get the patient's consent. You don't just do something and explain the problems later. Patients getting sicker AFTER your treratemnt is a fact of life and it occurs with ALL modalities of treatment, not just OMM. You'll learn more about that when yoiu get into medical school. Remember the word "iatrogenic"...you'll hear it over and over.
Also, there are some pretty common misconceptions about evidence-based medicine. EBM is not just about studies. It's about using ALL available information to come up with a diagnosis or treatment plan that will fit the individual patient. You use a wealth of information in making these decisions including past experience and intuition at some points. Remember that every time you prescribe a drug off-label that you are doing it because it has worked in the past for either you or a colleague but NOT because there are a bunch of studies that prove it works. The essential point in ANY treatment plan is that the patient be well informed of the possibilities and you make the decision to do it TOGETHER.
Lastly, there are a lot of things taught in medical school that no one has any idea why they work, but they don't stop teaching them. Drugs are the worst culprits. Yet, people still prescribe them year after year.
It's good that you want to look up some studies, but try not to get hung up on it. You'll have plenty of time to see it in action in your life. Just keep an open mind.