There are two internationally-recognised diagnostic systems for mental disorders which psychiatrists currently use in most countries of the world. One is the 10th revision of the International Classification of Diseases (ICD 10),[29] compiled and published by the World Health Organisation. The other is the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV),[30] compiled and published by the American Psychiatric Association. The respective teams of psychiatric researchers responsible for compiling successive editions of the ICD and DSM systems have cooperated closely in their work to ensure that the two systems maintain a high level of compatibility.[31] Whereas the DSM system is dominant in English-speaking parts of the world such as North America and Australia, the ICD is the main diagnostic reference in European and developing countries.
Both manuals define schizophrenia by describing the symptoms. After giving general outlines of the disorder they go on to supply definitive lists of criteria that must be identified in order to make a diagnosis. To determine whether a person has schizophrenia a psychiatrist will usually conduct an interview and listen to what the person says about their inner thoughts and beliefs. The psychiatrist will also make his or her own observations about the person's speech and behaviour. Reports and opinions of third parties, like relatives, will also usually be considered. From these combined sources the psychiatrist will make a judgement about whether the person's mental state fits the criteria specified in one of the diagnostic manuals. No other evidence is required beyond the subjective opinion of the diagnostician.
The manuals define schizophrenia as a type of psychosis. However, the manuals themselves admit there is some doubt as to what a psychosis is: ‘the term psychotic has historically received a number of different definitions, none of which has received universal acceptance.’[32] Nevertheless, there seems to be a core understanding that when delusions, hallucinations, disordered thoughts or extreme moods give rise to irrational behaviour, then psychosis is likely to be present.[33]
DSM-IV specifies that time periods should be taken into account when diagnosing schizophrenia: ‘The essential features of schizophrenia are a mixture of characteristic signs and symptoms (both positive and negative) that have been present for a significant portion of time during a 1-month period (or for a shorter time if successfully treated), with some signs of the disorder persisting for at least 6 months.’ In conjunction with these signs and symptoms there should also be a ‘marked social or occupational dysfunction’.[34]
Although clarity of consciousness and intellectual capabilities might still be present, symptoms include ‘characteristic distortions of thinking and perception’. These often take the form of delusions that ‘supernatural forces are at work to influence the affected individual’s thoughts and actions in ways that are often bizarre’.[35] In these circumstances the person might believe himself/herself to be at the centre of world-shattering events that are taking place around him or her.
‘Hallucinations, especially auditory, are common and may comment on the individual’s behaviour or thought.’[36] This leads to disturbances in thinking patterns and particularly in behaviour. To observers of a person with schizophrenia, the person’s thinking seems vague and when it is expressed in speech it is sometimes impossible to understand. There are ‘breaks and interpolations in the train of thought’,[37] and the person’s mood appears to be characterised by shallowness, ambivalence and inertia.
Delusions can be of many types and cover a variety of characteristic subject matter. Delusions may be persecutory, in which case the person might believe ‘he or she is being tormented, followed, tricked, spied on, or subject to ridicule’.[38] Alternatively, delusions can be referential, meaning that the person interprets certain signs and signals in the surrounding environment, such as bill-board advertisements or newspaper headlines, as being directed specifically at themselves and containing hidden messages. Or the delusions might be bizarre. Examples of bizarre delusions can include ‘a person’s belief that his or her thoughts have been taken away by some outside force ("thought withdrawal"), that alien thoughts have been put into his or her mind ("thought insertion"), or that his or her body or actions are being acted on or manipulated by some outside force ("delusions of control")’.[39]
Hallucinations may be associated with any of the senses but auditory hallucinations are particularly characteristic of schizophrenia. ‘Auditory hallucinations are usually experienced as voices, whether familiar or unfamiliar, that are perceived as distinct from the person’s own thoughts.’[40] These voices might take the form of presenting a running commentary on the person’s thoughts and behaviour, or they might enter into dialogue with the person’s own thoughts.
Disorganised thinking is also one of the definitive markers of schizophrenia. In diagnostic settings psychiatrists have to rely on patterns of speech to indicate this symptom. Speech can indicate the presence of disorganised thoughts in a number of ways: ‘The person may "slip off the track" from one topic to another ("derailment" or "loose associations"); answers to questions may be obliquely related or completely unrelated ("tangentiality"); and, rarely, speech may be so severely disorganised that it is nearly incomprehensible and resembles receptive aphasia in its linguistic disorganisation ("incoherence" or "word salad").’[41]
Disorganised thoughts and delusions may also affect a person’s behaviour so that it becomes irrational: ‘Grossly disorganised behaviour may manifest itself in a variety of ways, ranging from childlike silliness to unpredictable agitation.’[42] The person may find it difficult to carry out normal tasks necessary for day-to-day living concerning things such as meals and personal hygiene. Dress may become eccentric and behaviour may become inappropriate to situations in the form of indecent sexual displays, shouting and unpredictable shows of anger and agitation.
One of the more extreme forms of behavioural disorder associated with schizophrenia is catatonia: ‘Catatonic motor behaviours include a marked decrease in reactivity to the environment, sometimes reaching an extreme degree of complete unawareness (catatonic stupor), maintaining a rigid posture and resisting efforts to be moved (catatonic rigidity), active resistance to instructions or attempts to be moved (catatonic negativism), the assumption of inappropriate or bizarre postures (catatonic posturing), or purposeless and unstimulated excessive motor activity (catatonic excitement).’[43]
All the symptoms discussed so far fall into the category of ‘positive’ symptoms. Juxtaposed to the positive symptoms are a range of ‘negative’ symptoms. There are three principal negative symptoms: flattened mood, poverty of speech and avolition. Flattened mood ‘is especially common and is characterised by the person’s face appearing immobile and unresponsive, with poor eye contact and reduced body language.’[44] Poverty of speech is indicated by an inability to engage in useful communication while ‘avolition is characterised by an inability to initiate and persist in goal-directed activities. The person may sit for long periods of time and show little interest in participating in work or social activities’.[45]
Most of these symptoms, both negative and positive, are aspects of human expression that are on a continuum with normality. For instance, most of us have experienced symptoms like delusions at some time or other, by holding beliefs that proved to be false. This raises a problem for diagnosticians in that they must individually decide the point on a highly abstract and arbitrary continuum—extending from rationality to irrationality—at which normal false beliefs turn into pathological delusions. Since each patient displays personal variations of the characteristic symptoms the diagnostic process for schizophrenia is always at risk of inconsistency. To give some assistance to the standardisation of diagnoses both the ICD-10 and DSM-IV supply diagnostic guidelines which act as ready references to help reduce the otherwise excessive subjectivity of the process.
Next: DSM IV Diagnostic Criteria for Schizophrenia
[29] World Health Organisation, The ICD-10 Classification of Mental Disorders and Behavioral Disorders: Clinical Descriptions and Diagnostic Guidelines.
[30] American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders.
[31] Ibid., p. xxi.
[32] Ibid., p. 273.
[33] Ibid., p. 770.
[34] Ibid., p. 274.
[35] World Health Organisation, op. cit., p. 86.
[36] Ibid.
[37] Ibid., p. 87.
[38] American Psychiatric Association, op. cit., p. 275.
[39] Ibid.
[40] Ibid.
[41] Ibid., p. 276.
[42] Ibid.
[43] Ibid.
[44] Ibid.
[45] Ibid., p. 277.