The below comments are from the introductory abstract of the article "Induced Abortion and Increased Risk of Substance Abuse: A Review of the Evidence" written by Priscilla K. Coleman of Bowling Green University and published in Current Women’s Health Reviews...
Abstract: Research conducted over the last few decades has revealed an association between induced abortion history and substance abuse. The experience of induced abortion may be associated with psychological discomfort in some women and substance use offers a convenient remedy for alleviating the negative emotions without the necessity of disclosing the source of the discomfort. On the other hand, many characteristics related to the choice to abort are also systematically related to the likelihood of using substances (e.g., relationship difficulties, pre-existing emotional problems, a tendency to engage in risk-taking behavior, etc.)...
The full report can be read in a PDF file available at After Abortion.