Schizophrenia is characterized by a multiplicity of symptoms arising from almost all domains of mental function, e.g. language, emotion, reasoning, motor activity and perception.
These symptoms vary between patients, creating very diverse symptom profiles. The symptoms can include experiencing false perceptions (hallucinations), having false beliefs of control or danger (delusions), expressing disorganized speech and behaviour (positive formal thought disorder, bizarre behaviour), having impaired goal-directed behaviour (avolition), exhibiting blunted affect, being unable to find pleasure in activities or in the company of others (anhedonia/asociality), poverty of speech and thought (alogia) and impaired attention. The symptoms are often divided into positive and negative. Positive symptoms reflect an excess or distortion of normal function (e.g. hallucinations and delusions), while negative symptoms reflect a diminution or loss of normal function (e.g. flattening of affect and poverty of speech).
History of positive and negative symptoms
The nineteenth century English physicians John Russell Reynolds and John Hughlings Jackson first used the terms ‘positive’ and ‘negative’.
Reynolds (1858, 1861) discussed positive and negative symptoms within the context of epilepsy in a descriptive and theoretical way. Jackson (1931) suggested that they should be understood in terms of inhibitory processes. (The temporal relationship of these publications is misleading because Jackson was Reynolds’ contemporary, but his works were published posthumously.)
Disease is said to ‘cause’ the symptoms of insanity. I submit that disease only produces negative mental symptoms, answering to the dissolution, and that all elaborate positive mental symptoms (illusions, hallucinations, delusions, and extravagant conduct) are the outcome of activity of nervous elements untouched by any pathological process; that they arise during activity on the lower level of evolution remaining.
Jackson (1931) believed that the florid positive symptoms were a release phenomenon, occurring when underlying brain processes become disinhibited as a result of a pathological insult to a higher level of brain functioning, while negative symptoms represented a more generalized loss of functions.
While many of the pioneers of psychiatric phenomenology recognized the importance of negative symptoms, they did not use this term. For example, Emil Kraepelin wrote extensively about avolition and affective flattening as central and defining features of ‘dementia praecox’.
There are apparently two principal groups of disorders that characterize the malady. On the one hand we observe a weakening of those emotional activities which permanently form the mainsprings of volition… Mental activity and instinct for occupation become mute. The result of this highly morbid process is emotional dullness, failure of mental activities, loss of mastery over volition, of endeavour, and ability for independent action… The second group of disorders consists in the loss of the inner unity of activities of intellect, emotion, and volition in themselves and among one another…. The near connection between thinking and feeling, between deliberation and emotional activity on the one hand, and practical work on the other is more or less lost. Emotions do not correspond to ideas. The patient laughs and weeps without recognizable cause, without any relation to their circumstances and their experiences, smile as they narrate a tale of their attempted suicide. (Kraepelin 1919, pp. 74 - 75)
Eugen Bleuler (1911/1950) spoke of the ‘group of schizophrenias’, but argued that a single defining feature was present in all people suffering from the illness. This feature, a disturbance in the ability to formulate coherent thought and language (often referred to as ‘thought disorder’ or ‘loose associations’), was the most important of the ‘fundamental symptoms’. Bleuler considered these ‘fundamental symptoms’ to be present in all patients: loss of continuity of associations, loss of affective responsiveness, loss of attention, loss of volition, ambivalence and autism.
Bleuler held that these symptoms reflect underlying abnormalities in basic cognitive and emotive processes, while he relegated hallucinations and delusions to the status of ‘accessory’ or secondary symptoms.
Certain symptoms of schizophrenia are present in every case and in every period of the illness even though, as with every other disease symptom, they must have attained a certain degree of intensity before they can be recognized with any certainty… Besides the specific permanent or fundamental symptoms, we can find a host of other, more accessory manifestations such as delusions, hallucinations, or catatonic symptoms… As far as we know, the fundamental symptoms are characteristic of schizophrenia, while the accessory symptoms may also appear in other types of illness. (Bleuler 1911/1950, p. 13)
Kurt Schneider (1959) changed the focus of schizophrenia symptomatology with his assertion that the fundamental symptoms of schizophrenia reflect an inability to define the boundaries between self and non-self, resulting in experiences such as voices conversing or commenting, delusions of control or passivity, and thought withdrawal or insertion. He posited that these easily identifiable florid positive symptoms, which he called ‘first rank symptoms’, were the defining characteristics of schizophrenia (Schneider 1959). The clinical definition of schizophrenia shifted at this point to an emphasis on these positive or Schneiderian first-rank symptoms. A series of diagnostic tools were developed, such as the Present State Examination (Wing 1970), the Schedule for Affective Disorders and Schizophrenia (Endicott & Spitzer 1978), Research Diagnostic Criteria (Spitzer et al. 1978) and the DSM-III (American Psychiatric Association 1980), which defined schizophrenia according to a narrow band of positive symptoms.
However, clinical realties relatively quickly led to a corrective return to Bleulerian and Kraepelinian ideas, reintroduced as an emphasis on the importance of negative symptoms as central to the concept of schizophrenia. With this realization came three types of explanatory models attempting to account for the heterogeneity of the symptom profile in schizophrenia. These models include categorical, dimensional and unitary approaches to schizophrenia. Each model will be described in detail below.
R.L.M. Fuller, S.K. Schultz and N.C. Andreasen
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