Square Root:
The child being raised in an environment that is lacking one of the essential elements of the intact family, is ridden with instability rrlated to conflict, illness, and the like is apt to experience negative effects. This is universal, and it is not debated.
The couple that is engaged in the process of marital conflict, separation, and divorce is generally concerned about the effects on the children. But the judgment is that the kids will be better off when the parents are no longer fighting constantly. So they perceive divorce as the lesser of the evils. Sometimes they are right, and sometimes not. That the kids emerge with issues is almost always true.