It's not a chicken and egg argument of which came first. Treat abortion like the Telegraph's headline does. It's a risk factor for mental illness, just like it's a risk factor for breast cancer.
BREAST CANCER RISK FACTORS with references starts on page 25. The importance of reproductive factors in affecting breast cancer risk has been known for a long time. Women who have never given birth (or had a full-term pregnancy) are at a higher risk for breast cancer compared to women who have carried a pregnancy to term.(Page 26)
Think of it like smoking or obesity. They are just risk factors for assorted diagnoses. It doesn't mean any person will get those diagnoses eventually.
The two fall into vastly different spheres. Mental health is so tied to choices that it’s commonly called behavioral health today. Whereas there’s little that an unseen tendency to breast cancer could do to influence a woman to opt to abort her unborn child. Racial factors could tie into cultural factors to produce this sort of influence, but nobody has asserted this yet.
I’m not downplaying the seriousness of abortion itself (as far as I am concerned, it’s a killing that skirts the current system of law) by asking for good logic in asserting likely causative links. “Risk factor” is an easy way of dodging the causation question and doesn’t educate the prospective consumer of an abortion like a showing of causation would.