I think you just proved why it is always good to get both sides of an argument from the sides themselves.

2. Regarding generalizability of the sample, we clearly state in the article: “The study excluded first episode patients (who might have been less violent) and wholly treatment-refractory patients (who might have been more violent) and, thus, the findings cannot generalize to such patients . . . 7% of screened patients were excluded for this (or any other) eligibility criterion” (Swanson et al., 2006).

However, that’s not the whole story. We were concerned enough about generalizability that we went to the trouble to systematically compare CATIE participants with a quasi-random sample of 1413 patients enrolled in the Schizophrenia Care and Assessment Program (SCAP), an observational noninterventional study of schizophrenia treatment in usual-care settings in the United States — a study without the exclusion criteria that Grohol mentions. As we explain in the article, the two samples were very similar in their demographic and clinical characteristics — variables that might be considered risk factors for violence. In any event, this issue was addressed to the satisfaction of several demanding independent peer reviewers and editors for the Archives of General Psychiatry.

3. Regarding comparisons of violence rates across different studies: It’s important to note that the ECA violence measure (Swanson et al., 1990; Swanson 1994) included what the MacArthur study would have termed “other aggressive acts” as well as “violence.” Specifically, the ECA measure combined items indicating less serious acts (e.g. ” . . hit or throw things at your wife/husband/partner”) and more serious acts (e.g. “. . . used a weapon like a stick, knife or gun in a fight”). Using this measure, our ECA study found that 13% of persons with schizophrenia residing in the community had been violent within 1 year, compared with 2% of those without mental disorder. The ECA findings are not directly comparable to the CATIE findings, as Grohol notes. However, if one is going to compare them anyway (as Grohol does), the most correct comparison would be between CATIE’s 6-month prevalence rate for schizophrenia patients with any violence (19%), and the ECA’s 1-year rate for community respondents with schizophrenia with any violence (13%). Grohol’s assertion that there is a “difference of [only] 1.6%” between the CATIE schizophrenia and ECA general-community violence rates is specious; this is comparing serious violence in the former with all (minor + serious) violence in the latter. (Forget about apples and oranges; this is more like comparing a grape to a watermelon.)

Grohol also questions the ECA’s “magically low 2% figure” for the general population’s violence rate. Instead, he recommends using the MacArthur study’s “more recent and accurate data — research that uses the exact same violence measure — is readily available via Steadman et al. (1998).” Well, as I’ve noted above, the measures are not, in fact, the “exact same” (although I do think they’re fairly comparable — that is, if one includes “other aggressive acts” in the measure as we did in the CATIE combined index of “any violence”.) But if one insists, as Grohol does, that CATIE and ECA are NOT comparable measure of violence (notwithstanding that he compares them himself, when convenient), then MacArthur and ECA are not comparable either — for the same reason. You can’t have it both ways. (I think Grohol has opened himself to the charge of statistical sophistry here, though perhaps not the more serious crime of intentional academic mendacity!)

But the much bigger problem with using the MacArthur study to estimate the general community violence rate was clearly stated by the study authors themselves:

“Care should also be taken in making patient-community comparisons. We sampled from the census tracts in which the patients resided after discharge. Many of these neighborhoods were disproportionately impoverished and had higher violent crime rates than the city as a whole. We sampled in this manner to control for exposure to environmental opportunities for violence between the patient and the comparison groups. The comparison group was not intended to be an epidemiologically representative sample of the general population of Pittsburgh.” (Steadman et al., 1998).

That’s probably why the MacArthur study found such high rates of “violence” and “other aggressive acts only” in their community sample — 4.6% and 15.1%, or 19.7% combined, in a 10-week period. (Quite a bit higher, actually, than the schizophrenia sample in the ECA, let alone the non-mentally-ill sample.)

In contrast, the ECA violence study used a truly representative sample of community residents in 3 US communities, with a combined sample size of about 10,000. The MacArthur study enrolled 519 community residents from patient-matched census tracts in Pittsburgh. And the subjects were enrolled from acute inpatient units and followed in the community after discharge. About 17% of the MacArthur study subjects had a primary diagnosis of schizophrenia, while 24% had a primary diagnosis of substance use disorder. The point is this: the MacArthur study was never designed as an epidemiological survey of the prevalence of violence in persons with and without mental disorder in the community. That’s just not what it was, thought it’s often cited as such. Rather, it was designed to study violence risk assessment for patients discharged from acute psychiatric facilities. (As long as we’re talking about representativeness. . .)

4. Regarding our use of terminology in the CATIE study, let’s just consider the primary, ordinary-language definition of “violence” in the dictionary: “exertion of physical force so as to injure or abuse” (MerriamWebster.com). That would include stabbing somebody or shoving them against the wall. And of course there’s a difference between these kinds of two acts; that’s why we coded one as “serious” and the other as “minor” violence in CATIE. But also consider that the Bureau of Justice Statistics defines battery as a violent crime. And battery is mainly what we’re talking about — that is, acts that would qualify as battery if reported to the police. So if you want to know about all violence, we think the threshold should be set there.

Here is another way of looking at it: “Choking” is one of the behaviors the MacArthur violence interview asks about. So imagine that Smith and Jones both attempt to choke their respective spouses. Same intent, same reason — the only difference is that Smith is a robust 35-year-old-man, and Jones is a 75-year-old-woman with arthritis; Mrs. Smith receives a visible bruise to the throat and requires medical attention, while Mr. Jones is uninjured and just needs a cough drop. Now, the MacArthur study would reserve the term “violence” for what Mr. Smith did, but would not apply it to what Mrs. Jones did. We, along with the dictionary and the Bureau of Justice Statistics, would use the term violent to describe both acts, when speaking in general terms, while making appropriate distinctions between them when speaking specifically about severity and consequence.

The distinction between serious violence and minor violence is important, but so is the distinction between absolute risk, relative risk, and attributable risk. You can use the same epidemiological data (our ECA study) to support any of the following three statements: (1) The large majority of people with mental illness do not commit violent acts; (2) People with mental illness are more than 3 times as likely to commit violent acts as people without mental illnes; (3) About 3 percent of the violent acts committed in the community are attributable to mental illess as a risk factor net other causes or risk factors (Swanson, 1994). (Which of these statements you choose to emphasize may depend on the rhetorical point you’re trying make.)

5. Speaking of rhetorical points, finally, let’s consider the statement that Grohol quotes from a Treatment Advocacy Center spokesperson: “The CATIE violence study found that patients with schizophrenia were 10 times more likely to engage in violent behavior than the general public (19.1% vs. 2% in the general population).” The TAC statement seems to imply that our CATIE study enrolled a comparison sample of the general public and compared them to schizophrenia patients in an epidemiological study. We did not do so. Taken out of context, then, the TAC statement could indeed be misleading.

– Jeff Swanson

Steadman HJ, Mulvey EP, Monahan J, Robbins PC, Appelbaum PS, Grisso T, Roth LH, Silver E. Violence by people discharged from acute psychiatric inpatient facilities and by others in the same neighborhoods. Arch Gen Psychiatry. 1998;55:393-401.

Swanson JW. Mental disorder, substance abuse, and community violence: an epidemiological approach. In: Monahan J, Steadman H, eds. Violence and Mental Disorder. Chicago, Ill: University of Chicago Press; 1994:101-136.

Swanson JW, Holzer CE, Ganju VK, Jono RT. Violence and psychiatric disorder in the community: evidence from the Epidemiologic Catchment Area surveys. Hosp Community Psychiatry. 1990;41:761-770.

Swanson, JW, Swartz MS, Van Dorn RA, Elbogen EB, Wagner HR, Rosenheck RA, Stroup TS, McEvoy JP, & Lieberman JA. A National Study of Violent Behavior in Persons With Schizophrenia. Arch Gen Psychiatry, 2006;63:490-499.