Physician at Frankfurt (1763). City physician (1781). Physician of the Frankfurt orphanage (1782). First administrator of the medical institute founded by philanthropist Johann Christian Senckenberg. Published a demographic study of Frankfurt, Der Einwohner in Frankfurt in Absicht auf seine Fruchtbarkeit, Moralität und Gesundheit geschildert (1771).
Resided in Frankfurt all his life. Behrends’s son Johann Bernhard Jakob Behrends (1769- 1823) followed in his footsteps, becoming a renowned physician and anatomy professor.