Short answers, pulled from the story.
The robbery began on the 23rd of August 1973 and ended on the 28th of August 1973. Jan-Erik Olsson held four employees hostage inside Kreditbanken in Stockholm during this six-day standoff.
Swedish criminologist Nils Bejerot coined the term Norrmalmstorgssyndromet after the robbery concluded on the 28th of August 1973. He analyzed the victims from a distance without ever meeting or speaking to them directly.
Federal Bureau of Investigation analysis found that only 8% of over 1,200 kidnapping victims displayed signs of Stockholm syndrome. When excluding those with negative feelings toward law enforcement the figure dropped to 5%.
Stockholm syndrome has never been included in the Diagnostic and Statistical Manual of Mental Disorders since its inception due to a lack of formal clinical studies. Critics argue that symptoms fall under trauma bonding or post-traumatic stress disorder instead of being a distinct condition.
Lima syndrome describes an inversion where abductors develop sympathy for their hostages rather than the reverse dynamic. This concept emerged from the 1996 Japanese embassy hostage crisis in Lima Peru where most captives were released early.