To better understand schizophrenia, researchers have tried to find homogeneous illness subtypes characterized by a consistent clinical presentation and a comparable treatment response. Kraepelin proposed three clinical subtypes (hebephrenia, catatonia, and paranoia) based on clinical phenomenology that he thought were manifestations of the same morbid process characterized by early onset and progressive clinical deterioration.1 However, Bleuler believed that schizophrenia was a heterogeneous illness involving autism, ambivalence, and hallucinations and a number of morbid processes in association and affect.2 He added a fourth subtype of schizophrenia, simple schizophrenia, to those proposed by Kraepelin. More recently, Goldstein and Tsuang remarked that clinical description, longitudinal characteristics (ie, illness onset, premorbid history, and illness outcome), genetic endowment, biological markers, and brain abnormalities should be among the parameters studied in the search for homogeneity.3
In this article, by reviewing current data on the significance of obsessive-compulsive symptoms in schizophrenia, we address whether the presence of such symptoms brings characteristics sufficiently well defined to warrant the designation of a distinct subtype of schizophrenia. The clinical significance of obsessive-compulsive symptoms in schizophrenia has long been discussed in the literature, and there has been controversy over the implications of such an association.4"13 It has been suggested that obsessive-compulsive symptoms in schizophrenia have a prevalence rate of up to 60X,4"11-13 which is considerably higher than the prevalence rate of obsessive-compulsive disorder in the general population (3%).14 In addition, there is evidence that obsessive-compulsive symptoms in schizophrenia are not merely simple expressions of persistent psychosis, but rather that they constitute a distinct cluster of symptoms resembling obsessive-compulsive disorder.13 The next step would be to examine whether obsessive-compulsive symptoms in schizophrenia are manifestations of comorbid obsessive-compulsive disorder or whether they represent characteristics of a distinct subtype of schizophrenia.
CLINICAL PHENOMENOLOGY AND LONGITUDINAL CHARACTERISTICS
Early researchers thought that obsessions and compulsions were rare phenomena in schizophrenia and that these symptoms predicted a favorable outcome.4,5 More recent researchers, however, have found a higher frequency of obsessive-compulsive symptoms in schizophrenia.7"11-13 In addition, data indicate that patients with schizophrenia who have obsessive-compulsive symptoms may have a poorer outcome than patients with schizophrenia who do not have such symptoms.
In one study, Fenton and McGlashan found that 21 of 163 patients (approximately 13%) with schizophrenia had significant obsessive-compulsive symptoms. They showed that, compared with patients who did not have obsessive-compulsive symptoms, patients who had obsessive-compulsive symptoms were more socially isolated and had longer hospitalizations.7
Our group found similar results in a sample of patients with schizophrenia treated at a community mental health center.9 Approximately 25% of the patients had obsessive-compulsive symptoms. These patients, compared with those who did not have obsessive-compulsive symptoms, had an earlier onset of illness, were more socially isolated, spent more time in the hospital, had a worse employment history, and had lower global levels of functioning as judged by their therapists.9
Samuels et al. reported a similarly high prevalence of obsessive-compulsive symptoms in patients with schizophrenia (more than 20%) and found the presence of such symptoms to be an indicator of poor outcome. 10 Bermanzohn et al. reported that approximately 50% of the patients with schizophrenia from an inner-city day center had obsessive-compulsive symptoms.11 Although such high prevalence rates have led some to question the validity of these results, an increasing number of studies support the findings that obsessive-compulsive symptoms are frequently seen in patients with schizophrenia and that they may signal a more severe course of illness.7'9'10'13
Neuropsychological studies have played an important role in formulating hypotheses ahout the anatomic substrates of various psychiatric symptoms.15 They have also been useful in identifying cognitive deficits specific to certain psychiatric syndromes.15"19
The limited data regarding the neurocognitive function of patients with schizophrenia who have obsessive-compulsive symptoms suggest that obsessive-compulsive symptoms in schizophrenia are distinct from schizophrenic psychosis and that they are similar to obsessive-compulsive disorder.13
As part of a neurocognitive investigation, our group studied 30 chronically hospitalized patients with schizophrenia and found that 14 (45%) had obsessive-compulsive symptoms.13 Although the 30 patients were similar in age, dose of antipsychotic medication, intelligence, years of education, and severity of schizophrenic symptoms, those with obsessive-compulsive symptoms had more deficits in the cognitive areas previously found16"19 to be impaired in patients with obsessive-compulsive disorder who did not have schizophrenia (eg, delayed visual memory).13 In addition, although not associated with either positive or negative symptoms of schizophrenia, obsessive-compulsive symptoms were correlated with poor performance on those cognitive tests previously shown to elicit deficits in patients with obsessive-compulsive disorder (ie, the delayed visual memory and ability to change cognitive and motor tasks tests). The scores on these tests led to the correct classification of most (more than 80%) of our patients with schizophrenia into either the obsessive-compulsive or the non-obsessive-compulsive group.13
Treatment With Anti-obsessional Agents
Although it is widely accepted that obsessive-compulsive symptoms are often seen in schizophrenia and are indicators of poor outcome, their treatment has been only minimally studied. Evidence indicates that anti-obsessional agents improve the obsessive-compulsive symptoms in schizophrenia and may also improve the positive and negative symptoms of schizophrenia.20'21 Although relatively recent data on the treatment of obsessive-compulsive symptoms in schizophrenia are limited,21"24 there is evidence that anti-obsessional agents may improve the obsessive-compulsive symptoms in schizophrenia much as they do in obsessive-compulsive disorder.
Novel Antipsychotics and Their Implications in Schizophrenia
Unlike traditional antipsychotics, novel antipsychotics have dopamine-blocking properties and significant serotoninergic activity. They appear to be effective in the treatment of both positive and negative symptoms of schizophrenia.25 It has been reported that some novel antipsychotics may cause the emergence or exacerbation of obsessive-compulsive symptoms in patients with schizophrenia, perhaps because of their serotoninergic activity.26"30 These reports suggest that patients with schizophrenia who have obsessive-compulsive symptoms may respond differently to treatment with novel antipsychotics than those without such symptoms.
The clinical phenomenology and longitudinal characteristics suggest that obsessive-compulsive symptoms can be identified in a significant number of patients with schizophrenia, and that these patients experience schizophrenia at a younger age and have a worse outcome than do those who do not have obsessive-compulsive symptoms.7"11,13 In some studies, obsessivecompulsive symptoms have been sufficient to warrant a diagnosis of obsessive-compulsive disorder in 25% to 60% of patients with schizophrenia.8'10,13 These prevalence rates, which are considerably higher than those of obsessive-compulsive disorder in the general population, question whether obsessive-compulsive symptoms in schizophrenia are simply manifestations of comorbidity and support the existence of a distinct subtype of schizophrenia.
In addition, patients who have schizophrenia with obsessive-compulsive symptoms have different patterns of neurocognitive deficits and treatment response. Neurocognitive findings suggest that patients with obsessive-compulsive symptoms in schizophrenia have more deficits in those areas of cognition that had been found to be impaired in obsessive-compulsive disorder.13 Psychopharmacologic evidence suggests that patients with schizophrenia who have obsessive-compulsive symptoms may experience exacerbation of their obsessive-compulsive symptoms with novel antipsychotics26"30 and that they improve with adjunctive anti-obsessional treatment.21"24
Inferences from animal studies lead us to question whether patients with schizophrenia who have obsessive-compulsive symptoms may have suffered development alterations different from those of patients without such symptoms.31'32 During early development, lesions in the dopamine system, which is implicated in the etiology of psychosis,33-34 trigger abnormalities in the serotonin system, which is implicated in the etiology of obsessive-compulsive disorder,35"37 and vice versa.31,32 We hypothesize that, compared with patients who have schizophrenia but no obsessive-compulsive symptoms, patients with schizophrenia and obsessive-compulsive symptoms may have had more pervasive alterations during their development, affecting both the serotonin and the dopamine systems.
Although we do not have sufficient data to determine whether obsessive-compulsive symptoms in schizophrenia are expressions of comorbid obsessive-compulsive disorder or manifestations of different illness subtypes altogether, clinical phenomenologie, neurocognitive, and psychopharmacologic findings point toward the latter. Future family, biochemical, pharmacologic, and brain imaging studies may determine whether an obsessive-compulsive subtype of schizophrenia is theoretically and clinically valid.
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