The correlation is between diagnosis of ADHD and outcome parameter. IOW among adults with ADHD divorce rate is much higher, IIRC around 2 times the non-affected population rate.
The "causal" pathway is obviously complex, but bear in mind ADHD has a broad impact on functional domains, so an individual afflicted with ADHD will fail relationally, in education, employment, health and so on, one adversity compounding others.
For example, a married man loses his job because he can't get paperwork done, or keep schedules organized, which puts a strain on marriage due to financial stresses, eventually producing enough discord that the wife bails on the marriage.
The research on functional deficits has been going on a long time, and is well-vetted in peer reviewed journals. The confounds have been accounted for.
If you can't force yourself to keep attention on the road, you're going to crash. If you can't think about how that daily pint of ice cream will affect you beyond "it tastes good now", you're going to gain weight.
Heh, yeah. I've said that a few too many times. I'm just glad she understands.
A frequent pattern is that the "normal" individual becomes demanding that the affected partner performs better, which arouses the affected person's opposition and irritation.
Ultimately they become constantly angry at one another. Episodic or constant "warfare" is corrosive to the relationship which ultimately can't sustain the stress, resulting in failure of the relationship.
How does ADHD lead to divorce, motor vehicle accidents and injuries, and greater rates of general health conditions?
Is this correlation still present after controlling for confounders like education and economic status?