> [brainstim01:] No, but they asked for anecdotal data, and comparing how I progressed for the first year following the TBI versus the 2 years of brain stimulation and neurofeedback I am acutely aware of how much it helped.

I think observing a single individual in both untreated and treated time intervals provides some amount of control. It's not a terribly strong control, of course; one can certainly imagine scenarios such as that they were recovering the whole time, but that recovery hadn't reached a point where the effects became noticeable until the point where they happened to start the tDCS. So in the strong sense of "know", you're correct: they can't know for sure.

But to say that it provides no information at all is also wrong. The posterior probability that the treatment was helpful is greater, given these observations both before and after treatment was started, than if, for example, treatment had been started immediately. How much greater is hard to quantify, but a very substantial observed improvement suggests a significant effect.

This is actually a fairly standard way to design a clinical trial, called the "stepped wedge" design.

Everybody gets the control arm, followed by the treatment, but the time of the switchover is randomized, often in steps (hence the name). If people consistently recover at the same time relative to the treatment, but at different absolute times, then you can conclude the treatment works well.

Exactly. It's not an experiment you can run based on your own anecdotal experience.

I think I agree with everything here. I'm not saying no useful information can be derived. However the risk of the placebo effect or just general healing are hard to rule out on the limited information here. (Maybe OP's brain injury was slowly healing for a year but cognition gains didn't manifest until year two. I don't study brain health and we don't really have any information to make a judgement.)

The whole process has been frustratingly slow. To give some reference: The cognitive recovery was not linear. For the first 6 months I couldn't consume any content. No TV, no music, no internet news. Either the stimulation was overwhelming and/or I couldn't process the information I was receiving. After 14 months I couldn't watch any TV show that was new content, only things I have seen before many times (Simpsons, South Park, etc). After 24 months I could start reading but memory and recall were still very poor. 36 months after I'm able to read and watch new content with moderately successful retention.

It's good to hear you've made great improvements. If it makes you feel any better, part of your retention may just be a product of being older heh.

While I appreciate the sentiment I doubt the age difference between 31 and 34 account for the retention falls under the 'being older' category.