How old is the research, does it take into account the amount of time spent boarding? Age they start boarding correlated to issues developed.
Significantly in OPs case boarding is Monday to Friday so quite a decent balance of family to boarding time. Her Children were given agency in the decision, which is crucial, they were 11 when they started, which is not as young as we like to pretend in this society. They have long holidays at home with their parents.
Full board from a very young age, I can totally see messing you up. Back in a time when your only way of communicating with home being letters, or maybe a weekly call. Absolutely.
Weekly boarding during term time, for pre-teens and teens, focus on hobbies and study, no travel, friends on hand. Parents on speed dial, if you need a chat, or pictures sent back and forward. Sounds like for the right children a good balance.
Lets face it, half my friends kids are in breakfast club at 7.30 and collected from after school club at 6. They do a hobby, homework, eat dinner and go to bed. While parents are juggling full time jobs, childcare, house management....maybe even a small amount of time to themselves for exercise to connect as a couple if they are lucky.
Who knows maybe if all older children who wanted it could go to boarding school with their friends during the week everyone would be less stressed and able to actually enjoy time together.