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Mentalising impairment as a trait marker of schizophrenia?
- Esther Pousa, Ada I. Ruiz, Hospital del Mar, IMAS (Barcelona); Anthony S. David, Institute of Psychiatry (London) (6 December 2007)
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Esther Pousa, Clinical Psychologist Psychiatry Department, Parc Taulí Hospital (Barcelona, Spain), Ada I. Ruiz, Hospital del Mar, IMAS (Barcelona); Anthony S. David, Institute of Psychiatry (London)
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epousa{at}tauli.cat Esther Pousa, et al.
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One of the most controversial issues in Theory of Mind (ToM) research in schizophrenia in recent years has been whether ToM impairment may be seen as a trait marker or rather linked to particular symptoms. In their recent quantitative review of the literature of ToM in schizophrenia, Sprong et al. (2007) conclude that evidence to date seems to favour the notion that mentalising impairment represents a possible trait marker. We believe that their meta-analysis is an excellent piece of scientific work but that this conclusion should remain tentative. First, the existing evidence on ToM abilities in remitted patients is limited and difficult to interpret due to methodological shortcomings, such as non-explicit criteria for remission and poor control of cognitive abilities in the experimental design. A recent study by our group revealed that as a whole, stable patients did not show ToM impairment as compared with carefully matched non-psychiatric controls. When standard consensus criteria for remission were applied to the sample, half failed to meet criteria for remission and showed a significantly worse ToM performance than remitted patients and controls. Specific ToM deficits in this group were associated with delusions. Thus, specific ToM impairment could go hand in hand with the presence of symptoms (Pousa et al., in press). Second, findings of ToM impairment in schizophrenia high risk groups seem to support the assumption that ToM deficits represent a trait marker of the disorder. However, since these studies are mostly correlational, it is possible that the continuity of ToM deficits among “at risk” groups may in fact derive from an intrinsic relationship between a psychotic symptoms continuum and ToM impairment. A review of the literature of ToM and schizotypal personality traits reveals that studies finding a positive significant relationship do so mainly with respect to schizotypal positive traits such as the cognitive-perceptual and unusual experiences dimensions of the schizotypy instruments (for e.g. Pickup, 2006). Regarding investigations of first degree relatives, evidence is controversial (Sprong et al., 2007), with findings of impaired performance on the more common types of ToM tasks but not on the “eyes” test”. However, it should be noted from these studies that those controlling for sub-clinical symptoms or schizotypal traits conclude that the association may be linked exclusively to the presence of sub-clinical positive symptoms (Irani et al., 2006; Marjoram et al., 2006). In our opinion, the existing evidence in ToM research is still limited but the possibility of a state-like association should not be ruled out. The most methodologically sound means to explore this would be to carry out longitudinal studies comparing ToM abilities in different phases of the illness, defined by explicit criteria. Future studies also need to differentiate between the affective and cognitive aspects of ToM, since it is possible that these show a different pattern of relationship with symptoms clusters or schizophrenia profiles. Furthermore, it is possible that future research reveals that state-trait interactions may be occurring. |
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