Though her practice specializes in treating children, clinical psychologist Barbara Van Dahlen's greatest influence may be getting fellow doctors to give their time and expertise to help soldiers returning from war.
Concerned about the mental health consequences of the wars in Afghanistan and Iraq, she founded in 2005 Give an Hour, a national network of mental-health professionals like herself who provide free services for American veterans, their loved ones and their communities.
TIME honored Dr. Van Dahlen as one of the 100 Most Influential People in the World in 2012. Former Chairman of the Joint Chiefs of Staff Admiral Mike Mullen said of Dahlen: "Barbara has tenaciously attacked the epidemic of post-traumatic stress disorder, helping break through the stigma that prevents many from seeking help. She has also created an opportunity for many who have not served in uniform to make a difference."