More peer-reviewed evidence
The January 2003 edition [58(1):67-79] of the Obstetrical and Gynecological Survey contains a review article by John Thorp, MD; Katherine Hartmann, MD, and Elizabeth Shadigan, MD, as mentioned (see below) in the Washington Times letter by Dr. Colliton.
The abstract of the article, "Long-Term Physical and Psychological Health Consequences of Induced Abortion: Review of the Evidence", summarizes part of its findings as follows:
"Moreover, induced abortion increased the risks for both a subsequent preterm delivery and mood disorders substantial enough to provoke attempts of self-harm."
You can access the full text of the article online, but you have to pay for it. The three co-authors are on the faculty of the Department of Epidemiology, School of Public Health, University of North Carolina, Department of Obstetrics and Gynecology, School of Medicine, Chapel Hill, NC (Thorp and Hartmann) and at the medical school at the University of Michigan in Ann Arbor (Shadigan).