Ashli at S.I.C.L.E. Cell links to an article by Daniel Allott in the American Spectator where he discusses abortion and depression.
Another study in the non-partisan American Journal of Drug and Alcohol Abuse reported an increase in substance abuse experienced by post-abortive women. Women who had no history of substance abuse prior to their first pregnancy were, on average, twice as likely to abuse alcohol, more than twice as likely to abuse marijuana, and nearly three times as likely to use cocaine, as women who did not abort. In fact, there have been dozens of recent studies confirming the strong association between abortion and subsequent drug and alcohol abuse, which, in turn, are strongly correlated with depression.....
What this means is that if a woman who gave birth as a teen was depressed years later, it was usually due to dire financial straits or relationship problems and not to the fact that she bore a child at an early age. Conversely, if a woman who aborted her first child as a teen was depressed years later, it was probably not due to financial difficulties, poor physical health or a negative sense of efficacy. Instead, her depression could be linked directly to the abortion experience itself.
Also, I found that on average, all else being equal, a woman who aborted at or before the age of 20 had a depression score 15 percent higher than a woman who did not become pregnant as a youth.