In 2013, he was re-elected for a second term, while Ruth Vatvedt Fjeld was elected as the new Pro-Rector; she resigned the following year and was succeeded by Ragnhild Hennum.

[7][8] He was formally appointed as rector by the Government of Sweden on 27 April 2017 and assumed the position on 1 August, 2017.

[9] In 2019 Ottersen became a member of the Lancet–SIGHT Commission on Peaceful Societies Through Health and Gender Equality, chaired by Tarja Halonen.

He is particularly noted for his research on molecular mechanisms involved in the development of acute and chronic neurodegenerative disease, with a special emphasis on the role of cellular water balance and glutamate excitotoxicity.

In 2001, he, together with Jon Storm-Mathisen and Per Brandtzæg, was found to be the most-cited Norwegian scholar in international academic journals.