Joiner, Thomas. Joiner, Thomas E. Joiner, Thomas E. Jr Thomas Joiner is an American academic psychologist and leading expert on suicide. He is the Robert O. Lawton Professor of Psychology at Florida State University, where he operates his Laboratory for the Study of the Psychology and Neurobiology of Mood Disorders, Suicide, and Related Conditions. Joiner holds a Ph.D. from the University of Texas at Austin.