>> > First, it was not my idea to compare the incidence
>> of
>> PG (pathological gambling)
>> Arnie> True, but neither draws the conclusion which
>> Mackenzie does, that there is "zero evidence" for any
>> relationship between DAs and PG. Rather, they think it is
>> a real effect and are trying to put the rate of
>> occurrence
>> in context.
> it is either ok to derive meaning, or it is not. if it is
> ok for them to, then it is ok for me to, particularly when
> the datasets from which the meaning is derived are exactly
> the same, and when the authors have given the comparison
> of the two groups,, uncontrolled though they be, their
> blessing by comparing them in the first place.
> to say that the incidences are not appropriate for
> statistical comparison because they are derived from
> groups that are not controlled in any way, while at the
> same time sanctioning the authors?T direct comparison of
> those very same incidences, from the very same
> uncontrolled
> groups, is illogical.
Arnie> I should have made clear that I think the
investigators are also wrong when they make these
comparisons (between the prevalence of pathological gambling
(PG) among PD patients treated with DAs and the prevalence
in the general population), and for exactly the same reason.
But, when you make an incorrect judgment, it matters how far
you push it. Consider the following example. A and B are
investing in the stock market. Both are absolutely
convinced that Company X will announce next week that it is
going bankrupt. A has about 10% of his money in Company X
stock, which he decides to sell. B sells all of his other
holdings in addition to Company X and sells it short. It
turns out, of course, that Company X announces a fantastic
new discovery which revolutionizes its field. Rather than
dropping precipitously, its stock doubles and stays there.
Now, A has lost the opprtunity to increase his total
holdings by 10%, while B has lost everything.
A and B have made exactly the same incorrect judgment, but
the consequences are very different.
Getting back to DAs and gambling, both the investigators and
Mackenzie have made (in my opinion) the same mistake that it
is appropriate to compare the unadjusted occurrence rates of
PG in these two populations. Assuming for the sake of
argument that I'm right, the investigators would have to
make some minor editing in their conclusion statement. On
the other hand, Mackenzie's whole argument would crumble.
> But he then goes on to articulate a huge risk factor that
> could easily account for such a small difference:
> ?oIn addition, the availability of casinos in this
> retirement and vacation setting may allow subjects to
> discover this behavior after developing PD.?
> If one is going to derive significance from the variable
> age, for example, as you do, i.e., the PD gamblers are
> older than your average novice pathological gambler and
> therefore there is likely something other than natural
> inclination at the root of the onset of the behavior then
> one *must also* derive signifiicance from other
> variables,
> including proximity of casinos, history of depression, the
> fact that every single one of these people just underwent
> an
> adjustment to their meds (from which it would be logical
> to extrapolate that they have experienced a deterioration
> sufficient to require more meds - which is depressing!)
Arnie> I don't rule out the possibility that the
availability of casinos contributes to the occurrence of PG.
But there are many people who live in areas where casinos
are readily available but who do not become pathological
gamblers. Some of them engage in occasional "recreational"
gambling and some hardly ever gamble. This is exactly
analogous to alcohol, where we all have access to it, but a
relatively small percentage gets addicted. In fact, with
the development of Internet casinos, everybody has access to
gambling as well.
As I read the scientific articles, it does not seem to be
the case that these people start gambling "just" after an
adjustment in their medications. The rest of the argument
quoted above seems to be saying that the increase in PG
results from depression caused by a deterioration in their
PD symptoms. This would mean that it's not the drugs that
lead to PG but the disease itself. Aside from the fact that
I am not aware of any evidence to support this theory, all I
can say is: do you really want to make this argument?
More basically, my whole point is that we are not trying to
"account for a small difference". Rather, we are trying to
determine whether a totally different pattern of behavior is
related to Parkinson's drugs. The differences between the
two groups go a lot further than just age. Here is a
comparison showing how the groups differ:
Age: "Regular" PG: starts in teens or 20's.
PWPs: usually starts in 50s or higher.
Precipitating event: "Regular" PG: Usually, none.
PWPs: Follows an
increase in medication.
Rate of intensification: "Regular" PG: Builds up slowly
over years.
PWPs: Rapid
increase in intensity.
Other types of impulse control problems:
"Regular" PG: Alcohol/street drug abuse common.
PWPs: Frequently accompanied by excessive shopping,
hypersexuality.
Type of treatment:
"Regular" PG: Gamblers Anonymous or similar.
PWPs: Reduce drug dosage.
Effectiveness of treatment:
"Regular" PG: A lifelong struggle, relapses common.
PWPs: Quick and effective.
So, there are a lot of differences between the two groups.
There is no reason to expect that there would be any
relationship between the rates of PG in the two groups, so
the fact that both are around the same level does not tell
us anything. In particular, it does not tell us that the
causes of PG are the same in both groups, which is what
Mackenzie is arguing.
In my view, the last characteristic is the most convincing.
The fact that, even with only anecdotal data, not taking a
pill cures an addiction, is pretty strong evidence that
there is a connection between the pill and the addiction.
As it happens, I have just come across some additional
information which supports my argument. Just today, M.
Schild posted an abstract from the Journal of Geriatric
Psychiatry and Neurology. It turns out that the same issue
of that journal reports on a study of pathological gambling
in older adults (I don't usually follow this literature).
Although the number of subjects is small, they did not
develop their interest in gambling in their 50s and 60s.
Rather, as one would expect, they are people who started
their behavior at a much younger age and grew old with it.
They first started gambling at an average age of 27 and
began gambling once or more per week at an average age of
40.
Mackenzie, if you don't find this convincing, let's just
agree to disagree. I am getting tired of it, and the rest
of the list seems to have zoned out.
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