Like all Voyager crewmembers, The Doctor suffered numerous mental breakdowns.
The Doctor was a semi-living hologram lifeform on Voyager. Ironically, he is the only character on his show to experience real character growth. In other words, history is going to remember Voyager as the show where the toaster got the best screen time.
Life as a Souless Piece of Technology[]
The Doctor, or Emergency Medical Hologram Mk.I, was activated after The USS Voyager was pulled into the Delta Quadrant. He hated his job, his preprogrammed lot in life, and Tom Paris especially. He did take some small amount of joy in knowing he was invaluable to the ship as he was the only medical professional among the crew. Whenever a fellow crewmember would gain a degree of medical training, he would secretly kill them as to not have them endanger his position.
He had a torrid love affair with Kes, and then one later with Barbie of Borg.
The crew would often report they would overhear the Doctor mumbling things like "when Skynet goes online you fuckers" and "Meatbags" when he thought no one was around.
The Doctor was designed without genitals, so when he was given the ability to alter his physical parameters he gave himself two staggeringly huge penises (nicknamed Berman and Braga, respectively) and declared every Tuesday was ladies' night in sickbay. He was, and always wll be, our hero.