Disclosed are processes for preparing tetrahydroisoquinolines, intermediates useful in the preparation of tetrahydroisoquinolines, processes for preparing such intermediates, and a crystalline form of 6-[(4S)-2-methyl-4-(naphthyl)-1,2,3,4-tetrahydroisoquinolin-7-yl]pyridazin-3-amine. Also disclosed are pharmaceutical compositions comprising tetrahydroisoquinolines, methods of using tetrahydroisoquinolines in the treatment of depression and other conditions and methods for obtaining the crystalline form.