Wednesday, May 02, 2007

Grohol Slaps TAC Senselessly Silly

The Treatment Advocacy Center (TAC) recently posted that people with schizophrenia are 10 times more likely to be violent as compared to persons not suffering from schizophrenia. I quickly said "WHA?" That seemed so far detached from reality that I didn't even know where to start. So Marissa Miller had a nice analysis of their figures that pointed out a number of flaws in the analysis. Nice job, Marissa.

Then John Grohol stepped in and (BAM) slapped the TAC analysis silly. Absolutely senselessly silly. I won't even try to steal his thunder. Just go to Psych Central and you'll come away saying, "Those *@!@ at TAC!" Nice job slicing and dicing, Dr. Grohol! I'm always proud when a fellow psychologist throws the BS flag when needed.


Cairn said...

"So Marissa Miller had a nice analysis of their figures that pointed out a number of flaws in the analysis. Nice job, Marissa."

Actually, not quite, though it makes TAC look even worse in the comparison. In the way she is comparing absolute numbers of violent events, normal people are a bit over 5 times as likely to commit violence as someone with schizophrenia.

Here's how it breaks down:

Population = 300 million
1% of population has sz ==> 3 million people with sz.

No. of people without a mental illness = 150 million
2% of people without a mental illness commit a violent offense.
==> 2% of 150 million = 3 million w/o MI commit a violent offense.

She then makes a jump somehow equating the two 3 million numbers and saying TAC's claim of a ratio of 10 is wrong. There's an extra step that's required.

Of the 3 million with sz, 19.1% commit a violent offense. This gives 573,000 people with sz commit violence.

So as a ratio of absolute quantities, normal people are 3,000,000 / 573,000 = 5.2 times more likely to commit violence than someone with schizophrenia.


But put yourself in the role of a psychiatric nurse. At an intuitive level you would be very aware that 1 in 5 of your schizophrenia patients are capable of violence compared to 1 in 50 of the non-mentally ill visitors. The factor of 10 TAC uses has clear merit in this case.


What makes the difference is the mix of the population you interact with.

As two extremes, if you are only around people with schizophrenia and no people without sz, the 1 in 5 risk of violence counts.

If you are only around non-mentally ill people the risk of violence is 1 in 50.

The meaning of 1 in 5 being 10 times more than 1 in 50 is not clear to me since neither extreme is realistic. And TAC doesn't explain why this factor of 10 is of significance, though it obviously plays to their agenda.


Marissa Miller said...


I'll admit - I'm not a mathematician and I did the best I could. I purposely provided the disclaimer, "I could be wrong." But you figured out the stats for me and it seems that John Grohol kicked ass at breaking it down.

The point was to shed light on the fact that TAC's figures are wacked. Everyone else can get the accuracy down; I just wanted to point people in the right direction.

Stephany said...

I had a problem with TAC's "half of all" comment used for a stat. Half of what? TAC is good at using murder by mentally ill patients as a scare tactic that creates the very stigma NAMI wants to erase--and Torrey is supported by NAMI.
It's a strange connection if you really think about it. I've heard Torrey speak in person, and that guy is good at roping in an audience and when he talks about schizophrenia, he uses the word bipolar in tandem. I'm sure I sound like a broken record. But the guy believes Haldol is a good prevention as a anti-viral med for schizophrenia. He believes in forced med laws. Call me controversial, but I think he's on the way to "take Haldol to prevent the very virus that can cause schizophrenia." Prevention via medications. He believes everyone is exposted to the virus via cats, whether you owned one or not; the virus in in the air, in playgrounds, we are all at risk according to him. I've got the notes from his lecture. The guy called himself "delusional" many times. Everyone has an opinion, and I went with an open mind to that lecture and came out with the creeps.
TAC will use any stat whether they are correct or not, to get what they want: media hype that paints a large brush across all mentally ill patients and in the end stigmatizes all of us.