How much sleep do we really need to work productively?

If people are very different, isn't the conclusion there to figure out how much sleep you need to function effectively and ignore all the people who tell you how much you should need to function effectively? This is something you can measure and experiment with directly, and your results will be a lot more personally relevant than a blog post on the Internet.

Yes, there are bad doctors, and there are cursory or improper diagnoses, but that does not make the valid diagnoses any less valid, or the invalid diagnoses any more valid.

All doctors, from radiologists to orthopedic surgeons, are told not to self-diagnose, and psychiatric conditions are the easiest to improperly self-diagnose, even for trained professionals (which most people on HN are not).

On top of that, ADHD is one of the most difficult conditions to properly diagnose. Unlike more overt disorders, like schizophrenia, the symptoms are less clear-cut, and unlike more visible disorders, like (true) OCD[0], the symptoms usually lie two or three layers deep, making it easy to confuse the cause of the symptoms if you're not careful.

There exist differential diagnoses for this purpose (disambiguating the cause of the symptoms); most people just don't have them done, because they're incredibly expensive (several thousands of dollars), as they're very time-intensive on the part of the doctor.

That said, the entire claim which precipitated this discussion - that ADHD is somehow related to sleep deprivation - is completely preposterous. ADHD is perhaps inappropriately named, yes, but that suggestion is like saying that the cure to depression is to "stop being sad".

[0] I say "true" to distinguish clinical obsessive-compulsive disorder from the casual use of the term (eg, "oh man, my OCD kicked in when I saw Comic Sans mixed with Papyrus").

The 8 hours "myth" seems to come from the fact that most people sleep about that long when they don't set an alarm clock.

We are tuned by evolution.

The division here is between the underlying causes of the distractibility. And that's a pretty important distinction to make.

Many things can cause distractibility, from sleep deprivation to thyroid disorders. ADD/ADHD is only one of them. The effective treatment for any of these will not help the others. That is why the DSM-IV includes as a diagnostic criteria that you have to screen for other possible causes of the behavioral issues and rule them out.

The "many doctors" that you describe are simply not doing their job properly. By comparison the screening process for my son's diagnosis took about a month. Possibly not coincidentally I live in California - a state that has one of the lowest rates of diagnosis of ADD and ADHD. (Look at http://www.cdc.gov/ncbddd/adhd/prevalence.html to see your state diagnosis rate - I'd be suspicious of any diagnosis made in Alabama.) I am confident that my son's diagnosis is correct - my son has responded well to medication, while children without the disorder don't.

So here is my point again. If you're noticeably distractible and possibly sleep deprived, try getting more sleep. It might make a big difference. If you've actually got ADHD or ADD it won't hurt you, but it won't fix the problem either. There are other things that can also produce the same symptoms. Go to a competent doctor if you've got reason to be concerned.

Does anyone take into account the kind of activity done during the day?

For example, if I go on cycling trips, I can do perfectly fine with 4-6 hours of sleep per day. On the other hand, during revision times when I try to cram as much as possible into my poor memory, I tend to sleep a lot, i.e. 12-14 hours per day (and work/revise for about 6, tops). Under normal conditions, I still prefer 8-9 hours of sleep (and conversely ~10 of work).