There are a lot of scientific studies done from Buddhist practices. If you have heard of Jon Kabat Zinn, he helped to establish mindfulness in healthcare and treatment of disease and stress after building the Stress Reduction Clinic and the Center for Mindfulness in Medicine in the USA. And in Positive Psychology, there is a lot of emphasis on morality and virtue in increasing wellbeing (https://psycnet.apa.org/record/2003-04013-012
). Here is another paper on mindfulness research https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3679190/
Even though I only provided 2 scholarly articles, there are many, many research publications on the effects of mindfulness and meditation practice. Many more are emerging as mindfulness and meditation become more mainstream in the West now. However, the modern movement tends to separate mindfulness and meditation from Buddhism and also the basic tenets of morality such as the precepts. It would be more interesting if there was more research done specifically on Buddhism, but for now it seems like the mindfulness based practices, including meditation, which originate from Buddhism, are being researched and show up much more often in psychological interventions including modern-day counselling, therapy and stress reduction courses.
But ultimately, I think it's not up to you to convince your friends or anybody that Buddhism is the right way or to fix their doubts, unless they ask you directly to help them understand and want to know more. In my opinion, the best thing you can do is just keep practicing and let your own inner change be enough. If they see positive changes within you, they may get more curious to explore it themselves.