<P> During various episodes, Jareau has described growing up in a small town near Pittsburgh, Pennsylvania . When she was eleven, her seventeen - year - old sister Rosaline committed suicide by cutting . Rosaline's death was a particularly painful topic for her and she initially chose not to tell her young son about Rosaline, until her mother Sandy reminded her that avoidance was not the solution to dealing with the pain . A high school athlete, Jareau graduated valedictorian from East Allegheny High School, where she was the captain of the varsity soccer team her senior year and earned an athletic scholarship to the University of Pittsburgh . She also attended Georgetown, presumably for graduate studies . </P> <P> JJ decided to join the FBI after attending a book reading by BAU founder and then - Unit Chief Agent David Rossi . She once told Rossi that she had not known what to do with her life until she listened to his reading, which was held in the campus bookstore during her senior year in college . The next fall, she applied to the FBI Academy . </P> <P> In the FBI's Behavioral Analysis Unit (BAU), JJ acted as the team's liaison with the media and local police agencies . Though talented and helpful, she was not actually a profiler, having once declined Unit Chief Aaron Hotchner's suggestion to take the necessary classes in behavioral analysis . She works mostly out of the confines of the police stations and field offices the team visits . However, she does accompany the team on raids, and is proficient with firearms . This is made particularly clear when JJ resolves a hostage situation inside the BAU by killing the hostage - taker, Jason Clark Battle, with a single shot (Battle is a serial perpetrator of hero homicide, who lured Technical Analyst Penelope Garcia onto a date, and then shot her, in an attempt to keep his crimes from being discovered). During season six, JJ is given a promotion to the Pentagon; however, she returns in season seven as a full - time profiler, having received the necessary training . In season 9 ("200"), she is then kidnapped, and it is revealed that her year as the DOD Liaison at the Pentagon was a cover story . It turns out she was on a task force in Afghanistan, in search for Bin Laden . The team saves her, and in season 10, it is revealed she has PTSD, and hasn't been dealing with her ordeal being tortured when she was kidnapped, as well as 2 main events that happened when she was in Afghanistan, one of which includes her having a miscarriage, after a convoy was attacked . She tries to work through it with the help of Reid, who calls her on it when she disappears into the morgue one day, for almost a half - hour, after seeing herself on the table, in place of the victim . </P> <P> It is revealed in "JJ", that JJ had twice rejected a promotion to The Pentagon and hid the offers from her superiors . However, she is finally forced to transfer by "the brass ." JJ's departure reflects that Cook was let go at the beginning of season six, for financial reasons relating to the premiere of the spin - off Criminal Minds: Suspect Behavior . JJ's time at the Pentagon was revealed in depth in season nine . </P>

When did jj come back to criminal minds