I agree with you. These are really two different areas to study and clarify: What kind of woman has an abortion? (What are the REAL reasons?) What are the effects short and long term?
Your idea does point to abortion being pushed on women who are possibly the least able to cope with the trauma of it, if we were to establish that they probably already have either psychological or mental problems — or another large contributing factor is women who have been sexually molested, they are more likely to be sexually promiscuous. I’m not making any moral judgments why, that is just the statistic. So a woman who is emotionally vulnerable and already possibly in a more desperate state, gets convinced to kill her child, and it’s easy to imagine the results would be life-long and devastating.
I think this particular study is good in showing there are connections, but obviously I concur with you it’s not the definitive word on cause and effect and the why’s where-for’s.