Kander, who is 37, announced his decision Tuesday. The former Army intelligence officer said in a statement that he continues to feel the impact of PTSD, 11 years after leaving the military.

Kander says he contacted the Veterans Administration for help about four months ago but his condition worsened. He says he recently called a VA crisis line to say he has had suicidal thoughts.

Kander was seen as a likely favorite in the 2019 mayoral race. He was defeated by incumbent Republican Roy Blunt in Missouri’s 2016 Senate race.