[4] She held a postdoctoral fellowship from the MacArthur Foundation in the department of psychiatry at the Medical Center of Louisiana at New Orleans.

There, Hann participated in research related to early socio-emotional development in infants of adolescent mothers.

[3] Hann joined the National Institutes of Health (NIH) in 1991 as a program officer and chief of the Interpersonal and Family Processes Program within the National Institute of Mental Health (NIMH) Behavioral, Cognitive, and Social Sciences Research Branch.

[2] In that capacity, she provided leadership and management for the congressionally mandated Interagency Autism Coordinating Committee (IACC).

[2] In 2015, Hann became the associate director for extramural research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).