There seems to be a strange inconsistency that exists between the Doctor and other Time Lords when it comes to regeneration. It's definitely a continuity glitch of some sort. So we're going to see if we can fix it...
THE PROBLEM:
After listing all the different sorts of side effects that occur when the Doctor goes through a regeneration, it's time to address the Elephant in the Room. I attach this sort of title to the problem but I wonder if it's accurate. I seem to actually be the only person noticing it. In all my long years of fandom, I've never seen it discussed by anyone. Yet it seems to be so glaringly obvious.
The Doctor does seem to have a terrible time regenerating. At the very least, he/she goes through extended periods of unconsciousness after the process. At the very worst, he goes nearly mad and tries to strangle companions.
We've watched other Time Lords regenerate over the years. The first time we saw it happen was when the Doctor's Mentor regenerated in Planet of Spiders. His new body seemed ever-so-slightly shaky for his first few seconds. He even briefly stumbles through a line. But then he's fine.
And then there's Romana's regeneration. It's more like someone trying on different outfits than going through a turbulent metabolic process. To say the Time Lady deals with the transition with relative ease would be an understatement. She takes on Lady Astra's form, then a few other bodies and then goes back to Astra. Easily, the most complicated of all regenerations on the show. There should be all kinds of side-effects from something like that. But she moves on from the process with no hassle or fuss.
We might almost say that Azmael had a pretty rough regeneration in Twin Dilemma. After all, he doesn't survive it. But this only happens because he was in his last incarnation. So it's not truly a regeneration so much as it is a conscious willing of himself to death!
New Who shows us quite a bit of other Time Lords regenerating. After watching him steal several bodies in the Classic Series (and still experience little or no complications from it), the Master finally has a "proper" regeneration in Utopia. Technically, of course, he shouldn't be able to regenerate. Like Azmael, he had run out of lives back in the original run of the show. We can safely assume, though, that the Time Lords gave him a whole new cycle when they resurrected him for the Time Wars. The Doctor was pretty unsteady on his feet when he was given the same gift. He stumbled around all over the place during Deep Breath and acted very erratic. The Master seems to experience no real problems, though.
Then there's River Song (aka Mels) going through her regenerations with little or no complications. Yes, she does need some bed rest when she saves the Doctor at the end of Let's Kill Hitler but it's a pretty unusual scenario. She induces a second regeneration after only going through the process a few hours previously. She also uses up all her remaining lives to rescue the Doctor from certain death. That's bound to create some problems of some sort. But when she regenerates from that stray bullet earlier in the episode, she's doing just fine. We also get the impression she had no real issues with her first regeneration at the end of Day of the Moon.
Finally, there's the General getting shot at point-blank range by a staser in Hell Bent. He simply induces a regeneration, gets back up and dusts herself down as if she'd had an embarassing slip and fall rather than lost a life.
Are we seeing my point, yet? When the Doctor regenerates, it's this turbulent process that seems to almost put him/her through a physical and psychological meat grinder. He/she deals with all kinds of vicious side effects. But when other Time Lords go through the experience, they seem to do it with all the casualness and ease that one might have when changing their shirt!
Why does this happen? Why does the Doctor have so much trouble regenerating when other Time Lords don't?
There are a few arguments to explore...
FIRST ARGUMENT
The most obvious answer to this inconsistency is that the Doctor's regenerations are, oftentimes, very different from how other Time Lords regenerate. Most Time Lords live a quiet, sedate life in the Panopticon. They age very gracefully and just reach a point, from time to time, where the current body has grown too old and it's time to put on a new one. Whereas the Doctor, for the most part, induces regenerations because he's suffering from some type of fatal poisoning or has had a nasty fall or other such violent causes. If he/she wasn't regenerating under such extreme circumstances, things would probably go much easier for him/her.
Unfortunately, dismissing this argument comes far too easily. There are, at least, three occasions where the Doctor regenerates from old age. During two of those circumstances, he even declares that his current body is "wearing a bit thin". Which definitely implies that it's the passing of time that is prompting the latest change - not radiation from an arrangement of Metebelis crystals or some other such nasty situation.
On all three occasions, he experiences side effects after the regeneration. Doctor Nine's side effects seem the least obvious (he does appear to be behaving erratically during Rose but, admittedly, it's difficult to say). Doctors Two and Twelve, however, definitely seem to struggle through some problems. You might say that Two has a hard time because this is his first regeneration and he's just not used to the process, yet. You could also claim that Twelve's problems might stem from the fact that he is the first incarnation in a new cycle. But I would gauge these to be just extra influences that aggravate the situation. That, at the core of it all, the Doctor still struggles from the regeneration even when it occurs under more natural conditions.
On top of that, other Time Lords have been subjected to violent extremes that have precipitated a regeneration and they've not had complications. K'anpo/Cho-je got blasted by the mental energy of a Spider from Metebelis Three and walked away pretty unscathed. The General was shot by the Doctor but got back up from the regeneration and went on with her duties as if little had happened.
So the idea that the Doctor's regenerations are more complicated because they happen under difficult circumstances doesn't hold much water for me. I think there has to be another reason.
SECOND ARGUMENT
Our second argument actually ties in nicely with the first but adds an extra layer of its own.
There's quite an interesting implication that goes on during Deadly Assassin when the Doctor runs into Runcible at the Lord President's Retirement Ceremony. We get the impression both he and Runcible are about the same age. Runcible has heard something about the Doctor falling out of favor with Time Lord society and then asks him if he's had a face lift. This seems to insinuate that he doesn't believe that the Doctor can regenerate. That he was never granted the ability because he never actually became a Time Lord. The Doctor corrects him and explains that he has actually regenerated several times, now. The gesture backfires, however. Runcible seems a bit aghast that the Doctor has transformed so often. After all, he has a good idea of how old his former schoolmate is - he shouldn't have regenerated so much, already. "Well, if you will live such a rackety life!" he pronounces harshly.
Could this rackety life be part of the cause? As mentioned earlier, most Time Lords live out a quiet life on Gallifrey. Could all this mad running around that the Doctor does contribute to the problem? It wouldn't just be the stress of it all, of course. We also watch the Doctor put his/her body through all kinds of punishment. For instance: we've seen him expose himself to the vacuum of space without proper protective gear on during, at least, three different occasions (Four to Doomsday - The Doctor, The Widow, The Wardrobe - Oxygen). That's bound to put some real wear and tear on a body. And when the body must, at last, turn into a new one - could that sort of wear and tear make the whole process more difficult?
Tie that in with the idea that several regenerations have happened under violent circumstances and this theory really starts getting some traction. It's the Doctor's overall lifestyle choices that make regeneration so difficult for him/her. Had he just listened to Runcible, this wouldn't be such a problem!
Unfortunately, we've met a few other Time Lords (or half-Time Lords) who have also lived rackety lives. The Master being the best example of this. In fact, he's probably done worst things to himself/herself than the Doctor has. We've even seen him get shot during Utopia and recover from the regeneration with relative ease.
We can say much the same thing for River Song and all the punishment she puts herself through. Her love of excesses (sex and drinking) might also put greater strains on her body than what the Doctor has gone through. She's had violent regenerations, too. Hitler caused one of them by accidentally shooting her. Again, she emerges from the process with no real ill effects.
Argument Number Two also seems to be going down the plug-hole. Let's see if we can come up with something else.
ARGUMENT THREE:
This one has the most obscure reasoning. But it might just be the one that makes most sense.
It all stems from that great little row he and Romana had when they first met in Ribos Operation. Turns out Romana was, somehow, granted access to the Doctor's academic records. She points out, quite haughtily, that she graduated from the Academy with excellent marks. Whereas the Doctor scraped by with 51% on his second attempt.
We have also seen the Master gloat over the fact that he did better at the Academy than the Doctor. The Delgado Master picks on Three for getting weaker marks in their studies of Cosmic Science. "I was a late bloomer!" - the Doctor excuses himself feebly.
We can safely assume that most Time Lords do graduate with honors. That the Doctor might be the only one we've ever seen that just barely made it through school. This does seem to be the one great difference between the Doctor and his/her peers. So it could be entirely possible that his poor study habits are the cause of his turbulent regenerations. The two do, sort of, corroborate enough to make a legitimate connection.
River Song might be the only factor that clouds this particular argument. She never actually studied at the Academy. But the Silence may have gleaned all kinds of secret knowledge about Time Lords and some of it may have been comprehensive training on regeneration recovery. During the harsh conditioning she was put through to make her psychotic, she may have also been taught how to handle regeneration well.
Yes, rackety living and violent regenerations might contribute to the problem, but I do think the Ultimate Determining Factor for this is one of education. Had the Doctor paid better attention at school, regeneration might have been a far smoother process.
It really is as simple as that.