Something happened to my paragraph marks. I do apologise - as if my tedious exhalations aren't bad enough as it is...

[BM] So what are the discrete physiological causes of ADD popularly supposed to be, then?

[Projoy] Primarily temporal lobe dysfunction, at least according to Dr Daniel Amens who was one of the first to use brain scans to try and figure out what is different in an ADD brain. I've read his book Amens' "Healing ADD" where he describes the different areas of brain activation in the six varieties of ADD which he identifies. All of them share some degree of temporal lobe dysfunction.

The temporal lobe controls your ability to concentrate, and is more active when a brain is concentrating on something. A typical pattern in an ADD brain is that when it is used to concentrate deliberately on something then the temporal lobe is actually deactivated (ie there is less neural activity). I say "deliberately" because a common ADD behaviour is 'hyperfocus' where the brain will concentrate on something novel¹ to the exclusion of all else, but this is rarely deliberate.

Note that there is another book called "Healing ADD" by Thom Hartmann, that I would also recommend, but which is entirely different. In particular, Mr Hartmann specifically attacks Amens' work in scanning brains. But there we are.

[1] another very annoying aspect of this is that I cannot go to sleep if there is speech in earshot. I'll be drifting off quite satisfactorily when my brain will latch on to the interesting noises and amplify them in my perception. Similarly, I need silence or at least white noise if I need to think about a task which I am not entirely involved in, because otherwise my mind will concentrate on the novel rather than what I'm supposed to be doing.

Right, but that still leaves Raak's point unchallenged, doesn't it? There's nothing to suggest that there's a single cause for that particular pattern of brain activity.

Quite right.

For instance, even the mechanisms by which ADD brain patterns arise in the individual are not certain. There is a high correlation between ADD in parents and in their offspring (a figure of 70% is often quoted) which might suggest a genetic link, but it could equally be due to upbringing: the brain is plastic enough that learning will change its structure (no specific references, I'm afraid - I read this recently but can't remember where), and if much of a child's early development is achieved through mimicry then it's quite possible to imagine that parental ADD behaviours might imprint on the child.

It may well be that the role of genetics in mental development is overstated. There is some work (this book, for instance) which puts forward the argument that:

1. there is a common perception that genetic factors are the largest causative agent in mental illness
2. there is almost no evidence of a correlation between mental illness in children and in their parents (the book linked to states that the strongest correlation is in schizophrenia where there is a 50% correlation; nothing about ADD though)
3. if hypothesis (1) is wrong, then it must be environmental
4. the most pervasive environmental influence on children is their parenting
5. therefore the way you are raised is why your head works the way it does.

So, ADD may be at least as much a social phenomenon as a genetic one, although I also think that any learning which has this effect would have been at such a young age that there is no element of choice to it .