Complex sentence: Jeffrey A. Lieberman, a scientist and physician, has dedicated over 25 years to the study of the nature and treatment of mental illness, and is president of the American Psychiatric Association from May 2013 to May 2014.
Split into simpler sentences: Jeffrey A. Lieberman, a scientist and physician, has dedicated over 25 years to the study of the nature and treatment of mental illness. He is president of the American Psychiatric Association from May 2013 to May 2014.