I don't know anything about official studies, only my own experience.
I am an only child, and some of my earliest memories are of my parents arguing. No violence, just loud venomous arguments at least once a week. However, the idea of them getting divorced seemed like the worst thing in the world, even though I HATED the arguments and used to cry and stuff my fingers in my ears when they happened. After one of these arguments, I must have been about 6 or 7, my mum came to talk to me, and in an attempt to make me feel better said that maybe they wouldn't stay together much longer and then everyone would be happier. I remember my heart thudding to the ground and I begged and pleaded with my mum to promise me that they would never get divorced. I continued this begging and pleading quite a lot over the months, and I truly think it had a big effect on my mum and was probably a big part of the reason she stayed with my dad (who's selfish behaviour was probably the main factor in most of the arguments).
Now as an adult...my parents are still together, I think mainly because of finances and also just because they've got set in their ways and can't be bothered to make a change. But I look at them, especially my mum, and think "you don't belong together". They still argue, though less I think, but they don't really make each other happy on a consistent basis. And I feel guilty. Hugely guilty. Because I think if I wasn't piling emotional pressure on my mum she would have got out and made a better life for herself. Even though I know I would have found it very hard to accept at the time, I think my mum deserved better and I hate that she never went out and found it. And from my POV, growing up in a loveless atmosphere is just not good. I definitely think it affected my ability to form relationships and value them properly.
On the flipside, I am now a stepmum. My DP and his ex split up after 9 years together, when their DS was just one year old. He is now 6, and stays with us every other weekend and spends the rest of the time with his mum, her new partner and his half-sister (and step-sister too sometimes). We all have a good relationship, often spend time together as a blended family e.g. for his birthday and other social events. DSS isn't a perfect child (how many are?) but he is essentially happy, loves his little sister and also loves coming to us and being the only child too. He has a life surrounded by love, two homes full of love, half siblings, step siblings, parents, step-parents etc who love him and love each other. I look at what he has, and it convinces me that its better for parents who don't love each other to separate and find that love, rather than stay together just for the sake of their children.