هذیان های آزار و شکنجه: یاداوری تهدیدهای خصمانه اجدادی؟

Recent studies suggest that both the form and the content of persecutory delusional beliefs may reflect pathological exaggerations of evolved psychological mechanisms for dealing with social threat recognition. Here, we tested the hypothesis first put forward by Walston et al. [Evolution and Human Behavior 19 (1998) 257–260] that sex differences in the content of persecutory delusions reflect divergent ancestral hostile social threats, in a prospective study of two samples of German and Russian patients with delusions of persecution. Deluded men and women differed significantly in their attributions of perceived threats. The majority of men felt persecuted by groups of hostile strange males, whereas women projected their paranoid fears onto familiar people of their social environment, largely irrespective of psychiatric diagnosis or cultural background. In contrast to our predictions, however, both men and women with persecutory delusions were most frightened of physical violence. Fear of sexual coercion was only present in a small number of patients. In sum, this study is largely supportive of the hypothesis that the content of persecutory delusions reflects ancestral hostile threats.

Persecutory delusions have repeatedly been interpreted as the consequence of an evolved psychological mechanism of social threat recognition gone awry. Whereas the formal aspect of delusional beliefs of persecution has been linked to specific mistakes in inferring the intentions of other individuals (Charlton & McClelland, 1999) and to heightened vigilance toward threat perception in facial expressions of emotion (Green & Phillips, 2004), it has been suggested that the content of persecutory delusions could reflect threats from the human ancestral environment that differ for men vs. women: Walston, David, and Charlton (1998) proposed that women would project such delusional beliefs of being threatened onto female conspecifics, because for women, it was vital to cooperate with other nonkin women to build social support networks (Essock Vitale & McGuire, 1985). For men, by contrast, potential ancestral threats might have lain in marauding bands of strange males, because, due to strong resource competition between unrelated communities in ancestral human environments, men formed coalitions to defend territory and engage in warfare (Wrangham, 2004). In support of this proposal, Walston et al., (1998) found that women suffering from persecutory delusions felt threatened by familiar persons, whereas the majority of deluded men feared persecution by strangers. However, the sample size was fairly small, ratings were made in retrospect, the study did not examine the nature of the perceived threat (e.g., physical violence, sexual coercion, or ostracism), and there was no cross-cultural comparison, which could provide further evidence in favor of the hypothesis of pathologically distorted human universals for dealing with social threat detection in psychiatric disorders associated with persecutory delusions (Brown, 1991). In the present prospective study, we sought to address these open questions. Specifically, we hypothesized the following: (1) Men with persecutory delusions project their threat perception onto groups of strange males. (2) Deluded women feel persecuted by persons from their familiar social environment (both men and women). (3) Physical violence including death is the predominating nature of perceived threat in deluded men. (4) Women's fears focus on physical violence or sexual coercion if threatened by males, and ostracism if threatened by other females. (5) In light of the arbitrariness of categories of current diagnostic systems (i.e., DSM-IV 4th edition, American Psychiatric Association, 1994), these findings are expected to be independent of psychiatric diagnosis. (6) The anticipated sex differences are cross-culturally similar.

the German sample, 30 patients were diagnosed with schizophrenia, 14 with delusional disorder, 6 with schizoaffective disorder, 2 with affective disorder, and 5 with organic psychotic disorder. In the Russian sample, 50 patients were diagnosed with schizophrenia, 2 delusional disorder, 1 schizoaffective disorder, 1 affective disorder, and 9 organic psychosis according to DSM-IV ( APA, 1994). Five of the patients living in Germany from a different cultural background were classified as schizophrenic, one as schizoaffective, and one as organic psychotic disorder. The demographic variables of the samples are summarized in Table 1. The German and Russian samples did not differ with respect to age [F(2,120)=0.50, p=.61], sex distribution [χ2(1,120)=0.58, p=.47], or psychopathology ratings as measured using the PANSS [F(2,120)=0.17, p=.84]. Likewise, a multiple analysis of variance did not reveal any significant interaction between the diagnostic categories and nationality in terms of psychopathology [F(6,127)=0.35, p=.91] or age [F(6,127)=0.38, p=.89]. Table 1. Demographic data, diagnostic categorization, and psychopathology (as measured using the PANSS, Kay et al., 1989) of German and Russian patients with delusions of persecution Variable German patients Russian patients Statistics (p values) N 57 63 Age 44.95±14.7 46.38±12.04 .608, n.s. Sex (m : f) 25:32 32:31 .47, n.s. Diagnostic category Schizophrenia (N) 30 50 Delusional disorder (N) 14 2 Schizoaffective disorder (N) 6 1 Affective disorder (N) 2 1 Organic psychotic disorder (N) 5 9 Psychopathology PANSS positive symptoms 24.47±6.65 24.05±7.04 .93, n.s. PANSS negative symptoms 23.42±7.84 24.89±5.93 .284, n.s. PANSS general psychopathology 51.14±11.21 49.46±11.16 .689, n.s. PANSS sum score 98.67±21.11 98.35±19.93 .841, n.s. Table options As predicted, the majority of male patients (69.4%) with delusions of persecution projected their delusional fears onto strangers, whereas the majority of delusional women (68.3%) attributed their fears to familiar people. This sex differences was highly significant in the entire patient group [χ2(2,125)=24.42, p<.001], as well as in separate analyses in both German [χ2(2,57)=15.12, p<.001] and Russian patients [χ2(2,61)=8.70, p=.013]. Moreover, as expected, no difference between German and Russian patients emerged in respect of either female preference for familiar persons as perceived persecutors [χ2(2,58)=3.74, p=.15] or male preference for strangers as perceived persecutors [χ2(2,61)=1.81, p=.41]. We further hypothesized that males would feel persecuted mainly by other males, whereas females would be more likely to feel persecuted by other females. Overall, most males felt persecuted by other males (46.0%) or members of both sexes (52.4%). Contrary to our expectations, however, female patients with persecutory delusions projected their fears onto other females in only 17.5% of cases, whereas 44.4% felt persecuted by males and 38.1% by both sexes. Contrariwise, 10 of 11 patients who projected their delusional beliefs onto females were women. The difference between male and female patients was statistically significant [χ2(2,126)=9.77, p=.008]. Again, there was no difference between German and Russian male and female patients regarding the number of female persecutors [χ2(2,12)=1.53, p=.47], male persecutors [χ2(2,57)=1.28, p=.53], or perceived persecution from members of both sexes [χ2(2,57)=4.11, p=.13]. As regards the number of perceived persecutors, we predicted that male patients would feel persecuted by groups, whereas females would more often feel persecuted by single persons. Overall, 84.1% of male patients felt persecuted by groups; however, only 33.3% of female patients projected their fears onto single persons, the sex difference being nevertheless significant [χ2(1,126)=5.18, p=.023]. Interestingly, here, we found differences between German and Russian patients: In both nationalities, males felt persecuted by groups in 84% of the cases, but 53.1% of the German female patients felt persecuted by single persons vs. only 10% in the Russian sample. Thus, the sex difference in the entire group was due to the difference in the German sample [χ2(1,57)=8.31, p=.004], whereas in the Russian sample, no sex difference in the number of perceived persecutors was detected [χ2(1,62)=.44, p=.51]. We hypothesized that fear of physical violence would be more prevalent in male patients, and sexual violence in women. This was not the case. In the entire sample, men and women with delusions of persecutions did not differ in this regard [χ2(3,125)=3.27, p=.35]. In delusional men, the fear of physical violence was present in 85.3%; the percentage of female patients who primarily felt threatened by physical violence was even slightly higher (89.1%). The respective figures of males and females for fear of sexual coercion were 6.6% and 7.8%, for fear of ostracism 3.3% and 3.1%, and for loss of social status 4.9% in men and 0% in women. These figures were by and large similar in German and Russian patients, except that all German patients who feared sexual coercion were women (two patients were diagnosed with schizophrenia, two with delusional disorder), whereas the majority of Russian patients (80%) who felt threatened by sexual coercion were men. In addition, we hypothesized that, due to the imprecision of DSM-IV categories, no differences would emerge between diagnostic categories. Due to small N for schizoaffective, affective, and organic psychotic disorder, we performed statistical analyses in patients with schizophrenia and patients with delusional disorder only. As expected, the differences between male and female patients regarding the identity of perceived persecutors remained significant in patients with schizophrenia [χ2(2,83)=20.44, p<.001] and in patients with delusional disorder [χ2(1,16) =9.35, p=.002]. As for the sex of the perceived persecutors, the sex differences remained significant only in the schizophrenia group [χ2(2,84)=6.59, p=.037]. Regarding the number of perceived persecutors, no statistically significant sex difference emerged in either the schizophrenic [χ2(1,84)=1.92, p=.17] or the delusional disordered group [χ2(1,16)=3.31, p=.069]. Similarly, no sex differences were found in the nature of perceived threat in either group. These results are summarized in Table 2. Table 2. Summary of findings pertaining to the main hypotheses of the study in German and Russian patients with persecutory delusions German patients Russian patients Males Females Males Females Identity of persecutors Strangers 18 (78%) 8 (26%) 21 (72%) 10 (34%) Familiar persons 5 (22%) 23 (74%) 8 (28%) 19 (66%) (100%) (100%) (100%) (100%) Sex of persecutors Males 10 (40%) 12 (38%) 18 (56%) 16 (53%) Females – 6 (19%) 1 (3%) 4 (13%) Both sexes 15 (60%) 14 (43%) 13 (41%) 10 (33%) (100%) (100%) (100%) (100%) Number of persecutors Single 4 (16%) 17 (53%) 6 (16%) 3 (10%) Groups 21 (84%) 15 (47%) 27 (84%) 27 (90%) (100%) (100%) (100%) (100%) Nature of perceived threat Physical violence 22 (92%) 28 (88%) 24 (77%) 28 (90%) Sexual violence – 4 (12%) 4 (13%) 1 (3%) Ostracism 2 (8%) – – 2 (7%) Loss of social status – – 3 (10%) – (100%) (100%) (100%) (100%) Table options Finally, we were interested in which of the variables would best predict the odds of being a female or male patient with delusions of persecution. Therefore, we performed a logistic regression analysis fitting the identity, the sex, and the number of perceived persecutors as independent variables in the equation. All variables were significant zero-order predictors. Nagelkerke's R2 of the model was .297. The sex of 75.8% of male patients and 70.5% of female patients was correctly predicted on the basis of the model. The most significant predictor of the odds of being a female or male patient with persecutory delusions was the identity of the perceived persecutor [stranger or familiar person; regression coefficient B=1.693, exp(B)=5.436, p<.001]. The item “sex of the perceived persecutors” approached statistical significance [regression coefficient B=0.677, exp(B)=1.967 p=.052), whereas the number of persecutors (groups of single individuals) was not a significant predictor in the model [regression coefficient B=0.182, exp(B)=1.200, p=.75]. However, we found minor differences between German and Russian patients. In the German sample (values for the Russian sample shown in italics and square brackets), the identity of persecutors predicted best the odds of being a male or female patient. Of the male and female patients, 80.0% [80.6%] and 71.9% [57.1%], respectively, were classified correctly on the basis of the model. For “identity of persecutors,” the regression coefficient B was 1.317, exp(B)=3.731, p=.029, [regression coefficient B=2.339, exp(B)=10.366, p=.001]; for “sex of persecutors,” the regression coefficient B was 0.549, exp(B)=1.732, p=.311, n.s. [regression coefficient B=1.054, exp(B)=2.870, p=.105, n.s.]; and for the item “number of persecutors,” the figures were regression coefficient B=0.782, exp(B)=3.048, p=.154 [regression coefficient B=−1.921, exp(B)=.146, p=.086].