He has had his own private practice since 1977 and served as a speaker for the APA Assembly in both 2004 and 2005. He also served as President for the New York State Psychiatric Association from 1998 to 2002. At the New York County District Branch, Nininger established the first Task Force on Psychiatry and Nursing Homes, chaired the committee on aging for 14 years, and was among the first group of psychiatrists to volunteer services to the homeless. He volunteered at Pier 94 and Ground Zero with Disaster Psychiatry Outreach following 9/11 and in Louisiana following Hurricane Katrina.