In 2007, Dr. Stanton Jones and Dr. Mark Yarhouse published a longitudinal study of whether sexual orientation can change and whether attempts to change sexual orientation are harmful. InterVarsity Press has a number of helpful resources, including the paper that was read when the study was released in Nashville.
Read what a past president of the American Psychological Association had to say about the study:
Research in the controversial area of homosexuality is fraught with ideology and plagued by a dearth of science. This study has broken new ground in its adherence to objectivity and a scientific precision that can be replicated and expanded, and it opens new horizens for investigation…. I have waited over thirty years for this refreshing, penetrating study of an imperative, though controversial human condition. This book is must reading for psychotherapists and counselors, as well as academic psychologists studying human behavior and sexuality.
Nicholas A. Cummings, Ph.D., Sc.D., Former President, American Psychological Association; Distinguished Professor, University of Nevada, Reno; President, Cummings Foundation for Behavioral Health
The study has been updated with findings through 6-7 years and was just published in Journal of Sex & Marital Therapy.