Grey's Anatomy: Amelia's Brain Tumor Explains These 14 Crazy Plotlines

It's no exaggeration to say that Amelia Shepherd's (Caterina Scorsone) behavior has been a little off the rails since she joined Grey's Anatomy in Season 7. So off the rails, in fact, that the creators this season (under returning co-showrunner Krista Vernoff) opted to write in a brain tumor storyline for the character to explain some of her more bizarre moves over the past six-and-counting seasons on Grey's... not to mention on her previous show, Private Practice.

Amelia's told that her tumor has likely been growing for close to 10 years, and that every decision she's made in that time might have been affected by it. "The part of your brain that makes plans is compromised. Your plans, your judgment, your decision-making, your impulse control, it's all tumor," her doctor, Thomas Korracick (guest star Greg Germann) tells her. "You are not of sound mind now, and you haven't been for years."

Grey's Anatomy boss talks Amelia's brain tumor

But what exactly would fall under that umbrella? We decided to take a look at Amelia's actions over the past 10 years (i.e. the entire time she's been on Grey's - don't forget about that three-year time jump), to determine what role her tumor may have played in them.

1. Standing up to her boss, getting fired, and performing a miracle surgery. One of the biggest potential brain tumor red flags is Amelia's god complex as of late. But, as Private Practice fans are well aware, she's been (over?)confident for a while now. Remember when, in her first appearance on the show, she openly defied her boss Geraldine Ginsberg (Nora Dunn), got fired as a result, and went on to perform an experimental surgery on a surrogate mother against the wishes of the adoptive parents? Luckily, that all worked out in the end - the surrogate mother and triplets all survived, and Amelia eventually landed a job working with her former sister-in-law, Addison Montgomery (Kate Walsh).

2. Taking up smoking. Allegedly, Amelia's newfound habit was her way of dealing with the fact that her brother Derek (Patrick Dempsey) had been shot... despite the fact that the two of them were estranged. Hmmm. We'll take "Brain Tumor" for 500, Alex.

3. Sleeping with Mark Sloan. When Amelia goes to Seattle to visit Derek after he won't return her calls in the wake of the mass shooting, the Shepherd siblings relive the shared trauma of seeing their father get murdered during a robbery. Before she heads to the airport, Amelia sneaks in a quickie with her brother's best friend, Mark Sloan (Eric Dane).

4. Operating on a man while drunk. After an accidental sip of champagne that she thought was ginger ale shoved Amelia back into the throes of alcoholism, she started drinking behind her colleagues' backs and once even performed a surgery while drunk. Brain tumor? Maybe. But Amelia struggled with substance abuse issues for a long time before her tumor formed.

5. Trying to help her best friend commit suicide. This is a tough one, but arguably, Amelia's decision to defy her colleagues and assist in her best friend Michelle's (Sydney Tamiia Poitier) suicide - even though that's considered murder in California - could be blamed on her tumor. Though that attempt wasn't successful, Michelle's subsequent solo suicide, via an overdose, caused Amelia to start combining pills with her booze.

6. Dating Ryan. There's a whole subcategory of Amelia behaviors that may be the result of her addiction, or her tumor, or some combination of both. Entering into a relationship with her pill-snorting one night stand-turned-boyfriend Ryan (Wes Brown) - highlights of which included Amelia writing prescriptions for both of them, quitting her job at the practice, nearly getting arrested while trying to break into said practice, and eventually waking up next to Ryan's corpse after he died of an overdose - can probably be blamed on the former. But it's likely her tumor had some role in it as well.

7. Ditching her fiancé James and moving to Seattle. Amelia's colleagues on Grey's Anatomy have already started to speculate whether even her arrival at Grey Sloan in the first place can be blamed on her brain growth. As Meredith (Ellen Pompeo) noted in last week's episode: "She left a thriving practice and a fiancé in L.A. to come and live with her brother, who she resented. That was the tumor." And yeah, Mer's probably right. Amelia's transition from Private Practice to Grey's Anatomy came after she and her boyfriend James officially got engaged (offscreen, after Private Practice had ended) and she came to Seattle to get an idea of what domesticity was like by observing her brother Derek, his wife Meredith and their kids. After babysitting for less than 24 hours, Amelia decided she wasn't cut out for marriage and family life, had a nervous breakdown, decided to stay in Seattle, and broke up with James over the phone. Tumor alert!

8. Performing a risky operation on Dr. Herman. Amelia has already ticked off all the unsuccessful operations she's performed that need to be reviewed in light of her tumor diagnosis, but the one that fans will probably remember is, ironically, the one where she removed a seemingly inoperable brain tumor from her colleague, head of fetal surgery Nicole Herman (Geena Davis). Herman survived the surgery, but suffered a stroke that left her blind.

9. Acting hot and cold with Owen. At the start of their relationship (and really, throughout the entire thing, if we're being honest), Amelia has a pattern of drawing close to Owen (Kevin McKidd) and then pushing him away. Though she chalked it up to her fear of getting into another serious relationship, it was probably her tumor talking.

10. Not dealing with Derek's death. Granted, Amelia was abandoned by those closest to her (Meredith and Owen) in the wake of her brother's death, but throwing herself obsessively into work and cracking jokes about it in front of her (and Derek's) colleagues was probably not the best way to address her loss. She also came this close to using Oxy again, but luckily Owen talked her out of it. In a subsequent argument with Meredith, Amelia said that if someone had called her after Derek's fatal car crash, she may have been able to save him. There's that god complex at work again.

11. Almost leaving Owen at the altar... Once she and Owen decided once and for all to actually give a real relationship a shot, Amelia went full steam ahead, proposing to him after only a few weeks. Amelia's mother and sisters refused to come to the wedding, believing it to be yet another rash decision (ahem) on Amelia's part. After a brief Runaway Bride detour with Meredith and Maggie (Kelly McCreary), Amelia went through with the wedding...

12. ... and then leaving for real. Almost immediately, Amelia began to doubt her decision to marry Owen when they actually hardly know each other. A pregnancy scare, and the relief that she felt when the test came back negative, caused Amelia to question her long-held desire to have kids. She kept her feelings secret from Owen before walking out on him and leaving him a letter asking not to come after her. She moved in with Stephanie (Jerrika Hinton), and childishly avoided Owen both in and out of the hospital.

13. Giving Owen and Megan the cold shoulder. When Owen's presumed-dead sister Megan (Abigail Spencer) was found alive in Iraq and brought to Grey Sloan, she immediately began questioning her brother about his marriage to Amelia, since Amelia appeared to be throwing herself into work and avoiding quality time with Owen and his family at all costs. When Owen confronted her about it, she accused him of being in love with his best friend Teddy Altman (Kim Raver). There's certainly some truth there, as the two shared a kiss even before Amelia's accusations, but her awkward avoidance of Megan is probably tumor-driven.

14. Performing a risky jaw surgery. Amelia clashed with Jackson (Jesse Williams) early in Season 14 after going behind his back to perform surgery on a young boy that would require his jaw to be reconstructed (by Jackson). It was ultimately successful, but as Jackson pointed out, Amelia's arrogance on these risky surgeries has worked in her favor so far, but her luck will only hold out for so long.

Grey's Anatomy airs Thursdays at 8/7c on ABC.