These trends have been happening for decades and it tracks quite well the gradual breakdown of stable family structures. Psychologically for example, kids experience their parent’s divorce as worse than a parent’s death.
Correlation isn’t causation.
AFAIR there are studies looking at families with different cultural stances on divorce (but good luck controlling for other factors there). Also they tend to measure more easily measurable outcomes in the child than mental health, such as grades, which don't necessarily correlate.