Schizoaffective and Schizotypal Disorders
Ming T. Tsuang
William S. Stone
Stephen V. Faraone
Introduction
This chapter focuses on two disorders in the schizophrenia ‘spectrum’: schizoaffective disorder and schizotypal personality disorder. The emphasis includes the clinical features, classification, diagnosis, epidemiology, aetiology, course, prognosis, and possibilities for prevention for each disorder. Some aspects will be underscored to reflect controversial issues, such as the heterogeneity apparent in each condition. Such issues relate to the accurate classification of the disorders, which is important for at least two reasons. First, it is essential to develop reliable and valid diagnostic criteria in order to study the aetiology of the disorders and then utilize that knowledge to develop rational and testable intervention strategies. Heterogeneity adds variance to the process that reduces both the reliability of diagnosis and also the statistical power of experimental designs to detect intervention/treatment effects. Second, the development of newer generations of psychopharmacological treatments holds the promise of matching more appropriate and efficacious medications with specific syndromes or types of symptoms. This trend underscores the importance of differential diagnosis in determining what treatment a patient will receive. Heterogeneity within a diagnostic category complicates achievement of this goal. Another area to be emphasized involves the goal of early interventions, in addition to palliative treatments for these disorders. In contrast, other areas such as the genetic aetiology of schizoaffective disorder and schizotypal personality disorder, and treatments for schizoaffective disorder, will receive less emphasis here, to avoid redundancies with other chapters in this volume. Each disorder will be considered separately, starting with a review of schizoaffective disorder, the more severe of the two spectrum conditions.
Schizoaffective disorder
Clinical features
Schizoaffective disorder afflicts patients having schizophrenic and affective symptoms. Either they have affective symptoms of sufficient severity and chronicity to exclude an uncomplicated diagnosis of schizophrenia, or they show features of schizophrenia that are sufficient to exclude an uncomplicated diagnosis of an affective disorder.(1) These types of symptoms may or may not occur simultaneously, which underscores the importance of viewing the course of the illness longitudinally in addition to its cross-sectional presentation. Symptom clusters that are primarily affective or primarily schizophrenic predominate at different times.
Compared to patients with schizophrenia, patients with schizoaffective disorder often (though not always) demonstrate relatively high levels of premorbid function,(2,3) but nevertheless show significant premorbid weaknesses in multiple cognitive and clinical functions.(4) Patients with schizoaffective disorder also tend to show more identifiable precipitating events. The nature of the precipitating stressor may vary widely; for example it may be physical (e.g. recently giving birth or experiencing a head injury) or interpersonal (e.g. change in an important relationship). The clinical course of the disorder is often characterized by a periodic, rapid onset of symptoms that shows a relatively high degree of remission after several weeks or months. As Vaillant pointed out in the 1960s, many of these patients ‘recover’ completely after an episode, and resume their lives at premorbid levels of function.(5) As will be noted further below, the clinical features of some cases of schizoaffective disorder mainly resemble those of schizophrenia, while the features of other cases are more similar to those of bipolar disorder. Regardless of the subtype or variant of the disorder, however, the mortality rate is of special concern. Rates of death due mainly to suicide or accident show elevations in this disorder that are similar to those observed in schizophrenia and in major affective disorders.(6)
In general, schizoaffective disorder is more common in females than in males.(3) The age of onset varies, but tends to be younger than that of unipolar or bipolar disorder. Tsuang et al. found the median age of onset for schizoaffective disorder was 29 years, which was significantly lower than groups with bipolar or unipolar affective disorder, but similar to a group with schizophrenia.
Marneros et al.(2) also reported that a median age of onset of 29 years for schizoaffective disorder was lower than the median age for groups with affective disorders (35 years), but reported that it was higher than a group with schizophrenia (24 years). In contrast, Reichenberg et al.(4) reported no differences in the age of first hospitalization between patients with schizophrenia, schizoaffective disorder, or non-psychotic bipolar disorder. These differences between studies reflect differences in both the diagnostic criteria employed, and the heterogeneity of the disorder.
Marneros et al.(2) also reported that a median age of onset of 29 years for schizoaffective disorder was lower than the median age for groups with affective disorders (35 years), but reported that it was higher than a group with schizophrenia (24 years). In contrast, Reichenberg et al.(4) reported no differences in the age of first hospitalization between patients with schizophrenia, schizoaffective disorder, or non-psychotic bipolar disorder. These differences between studies reflect differences in both the diagnostic criteria employed, and the heterogeneity of the disorder.
Classification
The classification of schizoaffective disorder has always been controversial. Kraepelin reported in 1919 that patients with both affective and schizophrenic symptoms complicated the differential diagnosis due to the ‘mingling of morbid symptoms of both psychoses’. Kasanin first employed the term ‘acute schizophrenic psychoses’ in 1933 to describe a group of patients who experienced a rapid onset of emotional turmoil and psychotic symptoms, but who recovered after several weeks or months.(3) In other words, the symptoms appeared similar to schizophrenia during periods of exacerbation, but unlike schizophrenia, they showed a greater tendency to remit between episodes. These features sparked an ongoing debate by the 1960s about the proper classification of schizoaffective disorder. Much of this discussion involved the following proposals:
1 It was a type of schizophrenia (e.g. ‘remitting schizophrenia’);
2 It was a type of affective disorder;
3 It was a unique disorder that was separate from both schizophrenia and bipolar disorder;
4 It reflected an arbitrary categorization of clinical symptoms that masked a continuum of pathology between schizophrenia and affective illness;
5 It contained a heterogeneous collection of ‘interforms’ between schizophrenia and affective disorder (i.e. symptoms of both disorders).
The last possibility is not mutually exclusive of the first four; for example, one or more variants of schizoaffective disorder may be related closely to schizophrenia, while another may be related more closely to an affective disorder.
The puzzle has yet to be solved. Family and outcome studies provide useful ways of assessing the relative merits of each of the possibilities outlined above. These approaches are informative and will be reviewed below, although interpretations of such studies are complicated at times by the use of different diagnostic criteria across investigations.
(a) Family studies
Family studies provide an important tool for assessing the relationship between disorders. They are a type of genetic study that assumes that related disorders will co-aggregate more frequently among biologically related individuals than they would in the general population. Thus, a disorder is more likely to be in the schizophrenia spectrum if it occurs more frequently among the relatives of schizophrenic patients, compared with suitable controls. Similarly, a disorder is more likely to be in the affective spectrum if it occurs more frequently among the relatives of patients with affective disorders. Evidence for the inclusion of schizoaffective disorder in the schizophrenia spectrum is discussed in greater detail elsewhere (see Chapter 4.3.6.1). Only representative findings pertinent to the present discussion about the classification of schizoaffective disorder will be summarized here.
Bertelsen and Gottesman(7) summarized a series of seven family studies published between 1979 and 1993, using structured diagnostic criteria. Analyses of risk to the development of schizophrenia, schizoaffective disorder, and affective disorder in the first-degree relatives of patients with schizoaffective disorder, were included. In all seven studies, the relatives showed a higher risk of developing an affective disorder than of developing schizoaffective disorder. In five of the seven studies the risks of developing schizophrenia was equal to or greater than the risk of developing schizoaffective disorder. Thus, the relatives of schizoaffective patients showed generally higher risks of developing disorders other than the one with which they were diagnosed. These findings were consistent with a heterogeneous view of schizoaffective disorder, in which individual cases represented subtypes of either schizophrenia or of affective disorder. The findings were also consistent with the possibility that schizoaffective disorder represents a chance collection of ‘interforms’ between schizophrenia and affective disorder.
These findings were not consistent with the view that schizoaffective disorder represented a continuum between the other two disorders, because in that case, the rate of schizoaffective disorder in first-degree relatives would have been higher, compared with the rates at which these relatives developed schizophrenia or affective disorder. The findings were also inconsistent with the possibility that schizoaffective disorder represented a unique disorder that was independent of either schizophrenia or an affective disorder. In that case, the first-degree relatives of patients with schizoaffective disorder should show relatively high rates of schizoaffective disorder itself, but relatively low rates of the other disorders. In the series of studies reviewed by Bertelsen and Gottesman,(7) the morbid risk for schizoaffective disorder itself ranged from 1.8 to 6.1 per cent in first-degree relatives of patients with schizoaffective disorder, which was still higher than the rate observed in the general population (see the section on epidemiology below). These results, taken together with the higher risks for both schizophrenia and affective disorder, suggest that schizoaffective disorder is a heterogeneous condition. Recent reviews of family studies, including those that considered depressed (i.e. unipolar) and bipolar subtypes, have also underscored both the heterogeneity of schizoaffective disorder, and the controversial nature of its classification.(8,9)
(b) Outcome studies
A majority of outcome studies show that schizoaffective disorder has a better course than schizophrenia, but a poorer course than affective disorder.(10, 11 and 12) For example, Tsuang and colleagues reviewed 10 outcome studies reported between 1963 and 1987 that assessed patients with either schizoaffective disorder or schizophrenia.(10) Global, marital, social, occupational, hospital course, and symptom dimensions of outcome were measured. In each category, patients with schizophrenia showed poorer outcomes. In contrast, their review of 11 outcome studies comparing schizoaffective disorder with affective disorder showed that affective disorder was associated with equal or better outcomes on almost all dimensions. Thus, despite differences in methodology and diagnostic criteria,
schizoaffective disorder was frequently associated with clinical outcomes that were intermediate between those associated with schizophrenia and those related to affective disorder.
schizoaffective disorder was frequently associated with clinical outcomes that were intermediate between those associated with schizophrenia and those related to affective disorder.
Other researchers reported similar findings. Kendler et al., for example, showed intermediate levels of clinical impairment for schizoaffective disorder in an epidemiological family study.(13) Marneros et al. reported on outcomes as part of the Cologne Longitudinal study, using modified DSM-III-R diagnoses.(14) The outcomes were measured by symptoms in five dimensions (psychotic symptoms, reduction of energetic potential, qualitative and quantitative disturbances of affect, and other disturbances of behaviour) that persisted for at least 3 years. Consistent with the pattern described thus far, poor outcomes in the schizoaffective group occurred at a rate (49.5 per cent of the sample) that was intermediate between those observed in the schizophrenic (93.2 per cent) and affective groups (35.8 per cent), and differed significantly from both of them. In a more recent study, Jäger et al. studied 241 patients at the time of their first hospitalization, and then again 15 years later.(15) Similar to these other examples, schizoaffective subjects presented a clinical picture that was less impaired than the one shown by schizophrenic subjects, but more impaired than the one shown by affective subjects.
While these studies show schizoaffective disorder to have intermediate outcomes generally, there are categories in which it resembles schizophrenia or affective disorder more closely. For example, Samson et al.(10) and Reinares et al.(12) noted that outcomes for schizoaffective disorder were equivalent to those for affective disorder in several dimensions. Marneros et al., showed that 70 per cent of a schizoaffective group was rated as good or excellent on a measure of social adjustment, which did not differ significantly from 84 per cent of an affective group who received the same rating.(12) Both groups differed significantly from a schizophrenic group, however, in which only 44 per cent of the group demonstrated good or excellent outcomes. Moreover, the schizoaffective and affective disorder groups did not differ on a rating scale of psychological impairments (e.g. body language, affect display, conversation skills, and cooperation), although both were rated as significantly less impaired than the schizophrenic group.
Other studies, however, such as Kendler et al.(13) reported similarities between some types of psychotic symptoms in schizoaffective disorder and schizophrenia, including the severity of delusions and positive thought disorder, and the frequency of hallucinations. Each of these groups showed higher levels of these symptoms than an affective disorders group. Hizdon et al. showed recently that individuals with schizoaffective disorder did not differ from individuals with schizophrenia on basic cognitive measures of executive function, memory, and processing speed, although the schizoaffective group did perform better on measures of social cognition.(16) Reichenberg et al. showed that individuals with schizophrenia and schizoaffective disorder who were assessed premorbidly performed similar to each other but lower than individuals who later developed non-psychotic bipolar disorder, on tests of non-verbal and verbal intellectual function, and on tests of basic reading and reading comprehension.(4)
These overall differences in outcome serve to validate the classification of schizoaffective disorder as a separate syndrome further. Its heterogeneity, however, raises the issue of whether such intermediate outcomes might reflect the mean of a combination of mainly good and mainly poor outcomes. This in turn leads to the question of whether schizoaffective disorder can be subtyped in a useful and valid manner. If so, are better and worse outcomes associated with different variants of the syndrome?
Vaillant suggested in the 1960s that prognostic indicators, including a good premorbid level of adjustment, the presence of precipitating factors, an acute onset, confusion, the presence of affective symptoms, and a familial history of affective disorder (or the absence of a schizophrenic history), could predict remission in approximately 80 per cent of cases of ‘remitting schizophrenia’.(17) The inclusion of affective symptoms and a positive family history for affective illness on the list contributed (later) to hypotheses that variants of schizoaffective disorder were related to affective illness and to better outcomes. In contrast, variants associated more with schizophrenic symptoms or family history were associated more with schizophrenia and with relatively poor outcomes.(18)
There have been a variety of attempts to subtype schizoaffective disorders, based on whether affective or schizophrenic symptoms predominate. The validity of many of these attempts, however, is inconclusive. Bertelsen and Gottesman noted, for example, that at best, relatives of individuals with affective type schizoaffective disorder, or schizophrenic type schizoaffective disorder, showed only trends towards higher rates of affective disorder or schizophrenia, respectively.(7) Similarly, Kendler et al. did not detect different rates of schizophrenia or affective illness in first-degree relatives of patients with schizoaffective disorder when the patients were subtyped into bipolar and depressive subgroups.(13) Moreover, the subtypes did not predict differences in outcomes.
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