 |
Autism and Schizophrenia | |
| by Uta Frith
Extracted from the book "Autism - Explaining the Enigma" |
 |
|
| For
more comfortable reading and printing, make a download
of this file in MS Word format or text only.
|
In
popular speech disturbed behaviour is often called schizophrenic, in the
sense of ‘mad’. However, schizophrenia can be defined by using fairly precise
diagnostic criteria, and there are many different forms of madness. It
is a fact that schizophrenia, narrowly defined, rarely starts before adolescence.
Kraepelin, the discoverer of schizophrenia, reported that only about 6
per cent of his sample of over 1.000 cases had onset before age 15. The
onset of Autism, on the other hand, in almost all cases predates age three.
The time of onset of a disorder is of crucial importance. A disorder that affects the normal course of development from birth or even before, and the same disorder that begalls a mature organism are two different sorts of problems. Being born blind or deaf, for instance, leads to a totally different state of mind from becoming blind or deaf later. Similarly, psychosis of early onset is different from that of late onset. It is a remarkable fact that childhood ‘psichosis’ whose onset can be dated confidently after the third year of life and before age five is almost non-existent. It looks as if there is sanctuary period where a child can be said to be ‘protected’ from the outbreak of psychosis. Age of onset is not on a continuum, but is sharplydivided, notwithstanding occasional forays from either side of the dividing line. In genetically transmitted diseases just such a sharp division in terms of onset is a common pattern. It can be related to two different kinds of evolutionary pressure: the first to eliminate genetic deviance as early as possible, so as to allow the chance of a new, successful start; the second to postpone any deviance to a point as late as possible, since death from common causes might precede any adverse manifestations. If the psychoses were of genetic origin, then this patern would be readily comprehensible. What of those children who become psychotic after age five, but before puberty? Do their symptoms resemble Autism or do they resemble schizophrenia? The answer is straightforward: these rare children almost always resemble adult schizophrenics in their symptoms and can be easily distinguished from autistic children. This was established in an important population study by Kolvin and his colleagues in Britain, published in 1971(1). A study carried out in New York in 1984 by Green and others has essentially confirmed the earlier findings(2). Kolvin and his colleagues reported that the youngest child of their sample of 24 diagnosed as schizophrenic was 6.7 years old. In 80 per cent of the sample, the onset of schizophrenia was after age eight and a half. Even at age six, linguistic and cognitive development is substantially completed. The basic prerequisistes for adult competence are present, although performance improves with experience. Not surprisingly, then, childhood schizophrenia, even at age six, can be grouped with adult schizophrenia. There is no reason to confuse it with childhood Autism. In both Kolvin’s and Green’s studies, children with early onset, that is before age three, were compared with those of later onset. Some important differences were found that extended beyond behavioural symptoms. The New York study showed that 52 per cent of the autistic children scored in the severely subnormal range, that is, IQ below 50. In contrast, none of the schizophrenic children scored below IQ 65. In the British study, too, the schizophrenic children tended to be much more able than the autistic children. Thus, both studies confirm that Autism as a disorder of early development results in major intellectual deficit. Furthermore, in these studies low IQ was associated with direct evidence of brain dysfunction. The autistic group was also significantly more affected by adverse obstetric events. Despite the fact that schizophrenia and Autism are readily distinguishable diagnostic entities, in adulthood some autistic people resemble, in their surface behaviour, a certain type of schizophrenic patient. Such patients show negative signs, that is, little or no speech or facial expressions, and little or no interest in social contact or communication. They also exhibit simple movement stereotypies. However, behavioural resemblance is not dependable proof of resemblance in underlying dysfunction, let alone underlying causes of dysfuncion. Patients with positive schizophrenic symptoms in no way resemble autistic individuals even in their surface behaviour. The most characteristic positive symptoms of schizophrenia have to do with hearing voices and believing that there are significant personal messages in the environment. The voices and beliefs are subjective experiences which the patient is able to communicate to others. Articulate autistic people who have reported their experiences give accounts quite different from those of schizophrenic patients. Furthermore, in schizophrenia phases of acute illness often alternate with long periods in which normalty is established again. This pattern is not seen in Autism. It is, however, possible that schizophrenia and Autism can occur superimposed on each other. There have been some reports of such rare combinations(3). Given that the term autistic was first coined by Ernst Bleuler to apply thought processes in schizophrenia, and given that both Autism and achizophrenia result in some sort of social impairment, it is not surprising that the label ‘schizophrenic’ in the past was often used to refer to autistic people. To some extent, confusion between the two syndromes became self-fulfilling. Before the recognition of childhood Autism, some patients who would now be classified as autistic were described as schizophrenic with attention to their unique symptoms. Later, the old case histories might be cited as ‘proof’ that some schizophrenic adlts cannot be distinguished from individuals we now recognize as autistic. (1) I. Kolvin et al. (1971),
‘Studies in the childhood psycoses I to VI’, British Journal of Psychiatry,
118, pp. 381-419.
|
|