Symptoms, signs, and diagnosis of schizophrenia

[Pages:5]Symptoms, signs, and diagnosis of schizophrenia

The brain and mind are so fundamental to human activity their identity, autonomy, and mental capacity. 10% die by

that their diseases have preoccupied humanity for suicide.6 Their parents experience the illness as the loss of

millenia. Syndromes that we can recognise as forms of a previously normal child, who continues to live but

psychosis appear in the plays of Euripides and the seems a different person. One parent has described his

writings of Hippocrates. The disease that we now refer to experience of loss as "grief without end."'

as "schizophrenia" received its first widely accepted

delineation during the late nineteenth century under the Definition and clinical presentation

name "dementia praecox" in the writings of Emil Kraepelin.' His formulation separated it from manicdepressive illness and from dementia in the elderly, which

he later renamed Alzheimer's disease after its

neuropathology was delineated by his close friend and colleague Alois Alzheimer. Manic depression could begin early but had a remitting course, while Alzheimer's dementia shared chronic cognitive and social impairment but began at a later age. In the early twentieth century, Bleuler disagreed with Kraepelin's emphasis on chronicity and renamed the disorder "schizophrenia" to highlight the fact that the disorder produces a severe fragmentation of thinking and personality (schizo=split, phrenia=mind).2 Bleuler's name eventually stuck. One of the unfortunate

aspects of this label is that it tends to propagate

Schizophrenia may initially seem to be clinically confusing

because it affects so many different kinds of brain

functions. Perhaps the most striking aspect of schizophrenia is its sweepingly broad injury to a large array of cognitive and emotional systems in the human brain. The signs and symptoms of schizophrenia are diverse; they include disorders of perception (hallucinations), inferential thinking (delusions), goaldirected behaviour (avolition), and emotional expression (affective blunting), to mention only a few. No single one of those many signs and symptoms can be considered to be pathognomonic. Each is present in some patients, but none is present in all. Disorders of this sort are designated by nosologists as polythetic-that is, defined by many features, by contrast with disorders that are monothetic

misunderstanding about the nature of the disorder, creating mental images of "split personality". This rather sensational disorder (technically known as dissociative

(defined by a unitary feature). In this respect, schizophrenia resembles other complex medical disorders such as systemic lupus erythematosis, in that it damages

disorder) is relatively uncommon compared with the quietly tragic and more common disorder of

multiple brain systems and produces diverse signs and symptoms but is clearly recognisable as a syndrome. It

schizophrenia.

differs from most other mental illnesses, which are

The nosological validity of schizophrenia is well- typically monothetic, in that the latter seem to affect a

established, as is its public health importance. single brain system, such as Alzheimer's disease

Schizophrenia is a devastating illness, afflicting about 1% (memory), manic-depressive illness (mood), or anorexia

of the population worldwide.3 Its clinical presentation is nervosa (appetitive drive).

complex, but patients with this illness look essentially the same throughout the world, and a skilled clinician can usually recognise the classic forms of the illness even when unable to speak the patient's language and conduct a full interview. Although the course is variable and some patients do well, most continue to show some incapacity, often needing medications for the remainder of their lives and being unable to maintain gainful employment, complete schooling, or marry and have families. In 1980 in the USA, the cost of schizophrenia in terms of lost productivity was estimated at$20 billion, while the cost of continuing medical care and social maintenance was an

additional$11-1 billion. 4,5 The overall worldwide cost is

clearly an extraordinary multiple of these figures. The cost in terms of suffering of patients and their families is even greater. Schizophrenia is a disease of young people; it usually affects them in their late teens or early twenties, just as they are ready to achieve adulthood and begin their productive lives. Its victims often feel as if they have lost

The complexity of schizophrenia is so great that some early investigators challenged whether it could be defined with adequate precision to achieve good reliability among clinicians and investigators. Early cross-national studies suggested that there were international differences in breadth and style of diagnosis.'," In response to these studies, the World Health Organization and the American Psychiatric Association have produced criterion-based systems for diagnosing schizophrenia that have been shown to improve reliability substantially at both the diagnostic and symptom level. These are embodied in the most recent versions of their respective diagnostic

systems, the tenth International Classification of Disease

(ICD-10) and the fourth edition of the American Psychiatric Association's Diagnostic and Statistical Manual (DSM-IV).11,12 Those who developed these two

systems worked with one another to insure that

definitions would be sufficiently similar to produce good

international agreement. Structured interviews have also

been developed, which guide clinicians and investigators

to survey signs, symptoms, and course of illness in a

Lancet 1995; 346: 477-81

standardised manner to enhance reliability.13-17 Reliability

University of lowa Hospitals and Clinics, MHCRC, 2911 JPP, 200 Hawkins Drive, lowa City, IA 52242, USA (Nancy C Andreasen MD)

data from a recent study using a structured interview are shown in figure 1.18 The diagnosis of schizophrenia currently stands on very solid ground.

N Inter-rate (n=165)

Test-retest (n=162)

Figure 1: Comparative reliabilities of ICD and DSM criteria for diagnosis of schizophrenia

The core features of schizophrenia, as summarised in ICD 10 and DSM IV, are shown in table 1. The essential concept of schizophrenia in both systems is a disorder that is expressed through a wide variety of symptoms, including psychotic symptoms such as delusions and hallucinations, and abnormalities in emotional expression

or social interaction. These symptoms must be somewhat

persistent or chronic, and they cannot be explicable as secondary to some other recognisable medical condition.

While there are some substantive differences between

ICD and DSM, they are overall quite similar. Both select similar symptoms as characteristic features, including both positive and negative symptoms; both require that these symptoms be present for a sufficiently long time to rule out transient psychotic disorders; and both use exclusionary criteria to rule out psychotic syndromes that

occur in the context of mood disorders or that are

secondary to general medical illnesses (eg, frontal lobe tumours) or the effects of various psychosis-inducing substances (eg, amphetamines). The main differences between the two systems are the requirements of a duration of six months by DSM (compared with only one month for ICD) and of deterioration in functioning by DSM (not required by ICD). These differences make the DSM definition narrower. Although it is a national definition, DSM has had wide international usage, since criterion-based diagnoses were developed much earlier by the DSM system (originally in 1980, as compared with 1994 by ICD).19 Many clinicians throughout the world are accustomed to using DSM.

Simplifying the complexity: positive and

negative symptoms

Because the signs and symptoms of schizophrenia are so complex and diverse, an effort has been made to simplify thinking about the illness by subdividing it into natural categories. The most widely accepted approach is a subdivision into "positive" and "negative" symptoms. (Some of them are in fact signs, but are usually referred to as symptoms for shorthand convenience.) This terminology derives from Hughlings-Jackson, who discussed the positive symptoms of psychosis as being due to a release phenomenon, whereby symptoms from a lower level of evolution would break through because of the loss of some higher organising or governing brain region. Negative symptoms, on the other hand, were due to a simple loss of function, presumably a consequence of

neuronal loss. 20

Current reconceptualisations of Jacksonian ideas retain the distinction between positive symptoms as an exaggeration of normal functions (the presence of something that should be absent) and negative symptoms as a loss of normal functions (the absence of something that should be present). 21,22 They also draw on observations derived from cognitive psychology and clinical practice. The array of signs and symptoms classified as positive or negative is often summarised according to the range of cognitive and emotional domains involved, indicating that the two groups together include most brain systems or subsystems that are described in human beings. A summary of the symptoms and their corresponding cognitive systems or subsystems

is shown in table 2.

Clinical experience is also invoked to support the subdivison. Positive symptoms are typically those that call

attention to the illness and become the focus for acute

treatment. Patients usually come to clinical attention because their positive symptoms are clear indicators that they have a severe psychotic disorder. Negative symptoms may also be present quite early in the illness, but they become more notable during the later stages, often after the positive symptoms have remitted or diminished as a consequence of neuroleptic treatment. At present, positive symptoms tend to be more treatment-responsive than negative symptoms.23 Depite the diminution of positive symptoms with treatment, however, it is clear that the patient is still not well. Negative symptoms persist and produce the substrate from which impairment in social and occupational function grows. The negative symptoms

Table 1: Relation between cognitive systems and schizophrenic symptoms

Table 2: Diagnostic criteria for schizophrenia

478

[] Index (n=65)

[] One year (n=53)

jtjjj Discharge (n=65) tt Two year (n=40)

indicates, negative symptoms were as prominent at onset as the two groups of positive symptoms but the latter had remitted substantially at discharge and maintained this

status during a two-year follow up. Negative symptoms

tended to persist.

The original two-syndrome model proposed by Crow

suggested that positive and negative symptoms might be

due to a different pathophysiology; positive symptoms

were a consequence of overactivity in the dopamine

system, while negative symptoms were due to diffuse

neuronal loss that could be visualised by a structural

imaging technique such as computed tomography (CT).

Their differential response to treatment was thought to be

linked to these differential mechanisms.28 Although this

model has been largely abandoned as a method for

identifying subtypes of the disorder, its suggestion that

positive and negative symptoms may have prognostic

Symptom dimensions

value or provicie a guide tor identifying neural mechanisms is still viable.

Figure 2: Change in symptoms of schizophrenia in patients over

a two-year interval *Differs from ndex (p ................
................

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