Sorry for delay - life intervened.
how many people over 130 were included?
Curiously I can't find that figure. There were 5353 people altogether in the analysis sample (i.e., once they'd excluded the people for whom they don't have all the data - and the paper did attempt to check whether the group for whom they do have all the data is representative), and they do give means and SDs for IQ score in a wide range of subgroups, all of which look kind of normal, so probably whatever you'd expect for that size sample - what would it be? Not huge.
How much drug use was needed to be 'drug+' documented?
Used in the last 12 months (at age 30).
How much increased was the risk of the over 130 group to the next lower group?
The >130 group was between 1.1 and 1.8 times as likely to be using cannabis as the 115-130, depending on which group you look at (men, women, using IQ data from age 5, using it from age 10, with or without controlling for stuff). No very clear pattern within that except that all the ORs seem higher for the IQ-data-from-age-10 groups.
I wonder how good a job they did of controlling for SES. At my workplace everyone gets a drug test when they are hired, (although not routinely) but most people with my occupation never get a drug test - so I'm sensitive to the 'people with IQ under 107' are much more likely to have jobs with routine drug tests which means that Alcohol is much more favorable than Pot.
My impression is that occupational drugs tests are very rare in the UK, so I doubt that'd be a factor. They controlled for mother's and father's social class as assessed when the subjects were 5, and for subject's own: significant psychological distress (at 16), social class, monthly income, level of education (assessed at 30 years). Didn't seem to make much difference.
(Is it still current thinking that from a medical point of view Pot and Alcohol are quite similar? It's been so long since I've followed this question!)
No, I think that's an outdated view for two reasons. First, it's now consensus, I think, that the optimal alcohol intake is not 0 (for most people - might be different if you have a strong family history of certain cancers, etc.) but I know of no reason to think there's consensus that any level of pot intake is beneficial. Second, I think the evidence that pot, even in rather moderate quantities, can precipitate schizophrenia in vulnerable individuals is now pretty strong, and quite worrying.
