5-01: Dying Changes Everything
The title refers to 13 and Wilson in a literal sense and House in both a literal and metaphorical sense. 13 discovered in "Wilson's Heart" that she was positive for the Huntington's gene, and she is in fact dying (albeit slowly). That knowledge has colored her every action, her every reaction to things around her and has indeed, changed everything for her. Wilson is dealing with the death of his girlfriend, so for him, the death of a loved one changes his outlook, his interactions, his view of the world. House on the other hand, is not only dealing with his own guilt over Amber's death, but also how that death may cause another, more metaphorical death, that of his friendship with Wilson.
The team believes that the POTW is dying, and she is, until the final diagnosis of Lepromatous Leprosy, but along the trip, 13 and the POTW have many discussions on the meaning of life as well. The POTW has been living in the shadow of her boss, not realizing her potential, and 13's shortened life spurs her to try to push the POTW into seeking greater meaning in her life once she's better. The POTW gets fired, then resolves to make a mark, do something important, until her old boss asks her back. She then returns to her "normal" life, but 13 is still left with her pain. And House is unsuccessful at reaching Wilson, even with Cuddy's prodding to talk him out of leaving.
All deal with death in their own way, and in some ways dying does change things - at least it changes one's priorities.
5-02: Not Cancer
"Not Cancer" is a reference to an incorrect, literal diagnosis, but it's also a bit of a convoluted metaphor. Recipients of a donor are all dying, but not from cancers of the donated organs. Ultimately, it is determined that they are dying of cancers caused by cancer stem cells migrating to other organs making it "not cancer" obviously related their transplants. Given they actually were dying of cancer makes this title one of erroneous indirection. The metaphorical bent is based in House and Wilson's crumbling friendship. Wilson is walking away, i.e. taking the oncologist, the cancer doctor, out of reach. The friendship was a cancer, and it's not cancer.
5-03: Adverse Events
The title tracks events for House, for the team and of course for the POTW, which is a good place to start. The POTW creates adverse events for himself by taking far more chances than he should. He enlisted in multiple drug trials simultaneously, which, as a side effect, was stored in his stomach in a bezoar that allowed the drugs to be released into his system at odd intervals, causing distortions in his perception which created another type of adverse event. His altered state pushed him into a surrealistic mode of artistic expression which caused a client to brutally attack him.
The adverse events for the team are the result of House's investigation of their personal lives. House tries to find blackmail material on his team, but in the end only finds things that they'd prefer not to have made public, but in the end aren't useful for blackmail.
And the adverse event for House is that he never actually finds any truly incriminating information on his team, much to his chagrin.
The title refers again to both a literal connection (a large red birthmark on House's head that matches a friend of the family) as well as a figurative connection related to damage done at, or shortly following birth, or by extension, throughout childhood. This also harkens back to season 3's "One Day, One Room" when we found out about House's abuse from his father, which is referred to in passing from House's abject hatred of his father stemming from that abuse once he was secure in the knowledge that his "father" was not his biological father after all. Of course we didn't discover House's "inside" knowledge until "Birthmarks" aired.
Of course the title isn't only a reference to House, but also to the POTW who has a very significant "Birthmark" given her birth parents tried to kill her as an infant by pushing pins into her brain. Unfortunately for them, she survived, but that created a condition that caused nothing but problems for her, which of course House and team worked to correct. Again pointing to the fact that in her case, her actions were literally the result of a birthmark, and were not under her control. That also left the metaphorical birthmark in the psychological scar all adoptive children suffer, that of rejection. Her's was ultimately more severe than most. When she tried to find her birth parents, they spit in her face denying they ever had a daughter, but when it was later determined why they'd reacted that way, although we didn't see this explained to her, this would cause a more significant rejection scar.
5-05: Lucky Thirteen
This title is the antonym of the true meaning. Thirteen has been on a self destructive bent ever since finding out she's positive for the Huntington's gene and will develop the disease, but the POTW is hot, and Thirteen scored, so she was lucky in her romantic pursuit.
The title is literal, the POTW and his daughter cannot experience Joy, or any real emotion.
5-07: The Itch
To be added.
To be added.
5-09: Last Resort
To be added.
5-10: Let Them Eat Cake
To be added.
5-11: Joy to the World
To be added.
This time, the title connects to a goal, both for House and the POTW given they suffer from chronic pain, although in the POTW's case, it is intractable.
5-13: Big Baby
To be added.
5-14: The Greater Good
This time, the title refers to the POTW, and the team (and Wilson's) attempts to not only cure her, but to get her to resume her career for the greater good of humanity as a premier cancer researcher. Her goals are more personal, to enjoy her life pursuing the things of interest and meaning for her.
This title focuses on the religious side of faith. A priest who is unfaithful to his faith, and also a sexual connotation as the priest had been falsely accused of sexual misconduct, which, if true, would have been a literal lapse in faithfulness to his oath of celebacy.
5-16: The Softer Side
A connection to personality and gender in this case. In House, it's an external chemical change that causes a personality shift to his softer side. In the POTW, it's a reference to his/her gender resulting from genetic mosaicism, or confused DNA.
5-17: The Social Contract
This title is rather literal and refers to societal norms, specifically as related to personal interactions. The POTW is afflicted with a condition that removes his internal sensor and impulse control, so he says whatever pops into his head. This intrigues House, but the title also refers to the lack of a social contract in House/Wilson interactions. The basis of their friendship, at least from House's side is direct and unfiltered, which is counter to societal norms.
5-18: Here Kitty
The "Kitty" part of the title is key. The title refers to the cat in the episode, theoretially endowed with supernatural powers to predict death. "Death Kitty" might be more to the point, but "Here Kitty" works.
5-19: Locked In
This time, the title is primarily literal. The diagnosis for the POTW is Locked In Syndrome where he is literally locked in his body, with no way to get out, or to communicate outwardly.
5-20: Simple Explanation
This time, the title connects to House's quest, his yearning, his need to come up with a simple explanation for Kutner's death.
This is has a couple of somewhat literal connections in the episode. The POTW is an activist, a savior of the planet. Cameron is trying to act as savior with respect to her's and Chase's relationship, driving a wedge to save the relationship from taking a turn for the wrong reason.
5-22: House Divided
A psych reference this time, House literally divides, or his brain does. He starts hallucinating, seeing his best friend's dead girlfriend, but she's representing part of his brain.
5-23: Under My Skin
To be added.
5-24: Both Sides Now
This one is literal and metaphorical. The literal connection is to the POTW who had his brain separated to treat seizures, so there is no contact between the halves of his brain, and yet, they complete for dominance. In House, his brain again splits and forces him to confront the fact that he's disturbed beyond the point where he could address it himself. He needs to seek help outside of himself to bring himself back together, metaphorically speaking.