There has been much interest in the taxonomies used in medicine to define psychopathology, from the ideas presented by Adolf Meyer to those trying to improve the diagnostic and statistical manual of mental disorders (DSM). There has been clear criteria's set for each disorder of mental health however diagnosis is not as straightforward and often agreement over diagnoses is low. With diagnoses not being consistent across cultures (Barnes, 2008) and even the validity of classification labels being called into question due to the controversy surrounding the diagnosis of schizophrenia, it is evident that the medical model is far from perfect and possibly alternative approaches should be considered.
What is abnormal?
Many have tried to define abnormal using one-dimensional approaches; Cohen (1981) suggested abnormality is a deviation from the population norm such as a deviation in IQ from 100. Ahn et al. (2003) suggest incomprehensible behaviour is said to be abnormality and Szaz (1960) asserted that abnormal behaviour is behaviour that differs from the social norm. All these attempts of defining abnormality have their inherent problems. Lilienfield and Marino (2005) argued that abnormality cannot be absolutely defined and in fact the concept of abnormality is 'fuzzy' and has 'indefinite boundaries'. Lilienfield and Marino believe that abnormality is characterized by statistical rarity, being maladaptive responses to particular situations, involving impairment and leading to the need for treatment. These criteria's are subjective but with enough consensuses a particular behaviour could be defined as abnormal.
A dichotomy between normal and abnormal?
The medical model suggests a dichotomy between normal and abnormal mental states. It assumes that abnormal behaviour is a result of a physiological abnormality, so mental illness can be seen to be similar to that of medical problems. The only way for a dichotomy to be established is in the ability to classify symptoms of mental illness and thus forms diagnoses. Both the DSM and ICD adopted this philosophy which lead to classification systems. These classifications allowed clinicians to fit symptoms to a form of treatment. Diagnoses such as these are quite important when establishing drug therapies such as using anti-psychotics for schizophrenic patients. Incorrect diagnoses will lead to incorrect treatment or medication being administered which will lead to further complications in developing new treatments. However diagnoses have never been consistent this is evident in the ever changing, refining or evolving DSM. The DSM has gone through significant changes since its first iteration because of the inconsistencies of diagnosis. Chen et al (1996) studied these inconsistencies among patients who were originally diagnosed with schizophrenia and who were hospitalised a minimum of four times in a seven year period. It was discovered that 22% were then given a different diagnosis to that of schizophrenia and 33% of patients who were originally given a diagnosis other than schizophrenia were later diagnosed as schizophrenic. This examination was conducted during the DSM-III era, the DSM-IV improved diagnostic consistency across some conditions but couldn't be applied to disorders within the schizophrenic spectrum (Nathan & Langenbucher, 2003). Furthermore because of the inconsistencies of diagnosis, the ethnicity of a clinician can also influence that diagnostic approach. Mikton and Grounds (2007) found that in the UK, clinicians who were Caucasian were three times more likely to conclude that a patient had a personality disorder than African Caribbean doctors.
The idea of being mentally ill is binary; either an individual is mentally ill or is not. This somatogenic approach, mental abnormalities resulting from biological disorders of the brain, is core to the medical model and what differentiates it from other approaches such as the psychogenic approach; however this dichotomy between normal and abnormal is becoming harder and harder to uphold. Hearing voices within an individual's own mind is a defining characteristic of schizophrenia; however this abnormal mental state has been documented in a large number of individuals within the normal population. Should these individuals who live normal lives and were never considered to be abnormal be classed as mentally ill?
This approach also has an element of de-individuation, the model does not account for the experience of an individual rather the diagnosis is established and treated nothing more. This is evident in the idea that the medical model forgoes other alternatives such as psychological or social factors and only focuses on the biological factors which leads to only biological treatments being used. Farber (1990) argued that the medical model does not take into account the individual's ability to change and it cannot be assumed that inflexible biological factors lead to psychological states that differ from normal individuals. To conclude the diagnostic approach has it strengths and weakness and with refinement of aspects such as comprehensiveness, ease of use, clinical significance, reliability and validity; diagnoses can become consistent and become more effective. However should there be a dichotomy between abnormal and normal mental states? Should alternatives to the medical model be considered?
Clark et al (1995) have argued against the categorical approach found in the DSM, the dimensional approach offers a different perspective to the diagnostic system. The DSM assume mental illness is binary in approach, either an individual suffers from a number of symptoms such as depression and so on leading to a categorical classification which then leads to a disorder or not. The dimensional approach argues that categorical approaches to psychopathology are challenged by ideas such as co-morbidity and heterogeneity. Co-morbidity refers to the idea that an individual could suffer from criteria's for more than one diagnosis, similar to that of the transtheoretical approach. Heterogeneity refers to the ability of two individuals presenting with different symptoms but ultimately given the same diagnosis, this concern is highlighted in the diagnosis of schizophrenia. The dimensional approach considers abnormal and normal mental states be placed on a spectrum and individuals who suffer from a mental disorder or diagnosed mentally ill are considered to be at the extreme end of abnormal.
As stated before many individuals within the normal population have heard voices in their heads and many others have felt anxious or depressed at one time or another. These incidents are not exclusive to those individuals suffering from a mental disorder. What should be considered is how frequent and how intense these incidents are to conclude that an individual suffers from a certain disorder. Diagnoses formed using the dimensional approach is produced by having a threshold score and if an individual scores higher than this threshold and based on the severity and frequency of the incident, an individual can be given a diagnosis. This is approach circumvents the forcing of individuals into certain diagnostic categories which they don't quite fit into. The dimensional approach accounts for experiences not explained by the medical model, however does not specify the processes that cause a problem.
What is schizophrenia?
The diagnosis of schizophrenia is still one of the most controversial and debated topic amongst clinicians. Disagreement ranges from what causes the disorder (genetic or environmental) to treatment options (ECT or drug therapy) to even if the disorder actually exists.
The underlying mechanisms that cause schizophrenia is still unknown, or not agreed upon, however the consensus view is schizophrenia includes a few related disorders which are characterized by fundamental divorce of thinking and perception. Delusions and sometimes bizarre beliefs is also a characteristic of individuals suffering from schizophrenia. These could include delusions of grandeur, delusions of control and delusions of reference. The DSM states for schizophrenia to be diagnosed two or more symptoms (delusions, hallucinations, disorganized speech, catatonic behaviour and negative symptoms such as alogia or avolition) should be present for more than a month. The DSM goes further to state that there are four sub-types of schizophrenia; disorganized, paranoid, catatonic and residual. This classification system employed by the DSM has many benefits; however could this system be improved by combing recent, modern, knowledge with existing classificatory themes? That is, could reliability be kept, for the DSM diagnosis for schizophrenia, while still improving its validity?
Like other disorders, the DSM-IV describes schizophrenia as discrete category rather than a quantitative dimension. Depending on these discrete categories have its inherent problems for patients that have symptoms from multiple disorders because this could lead to increased rates of co morbidity (Frances et al., 1991). The dimensional model is not perfect with both conceptual and practical limitations (Millon, 1991), though does this approach have greater validity? Undoubtedly, the dimensional approach to schizophrenia is more consistent than the categorical approach because it uses polygenic models of inheritance to explain the familial transmission of schizophrenia and this is widely considered the best explanation for this inheritance (Tsuang et al., 1999). The polygenic model refers to the idea that a number of genes combine under certain environmental aspects to cause schizophrenia. It is due to both genetic and environmental factors that individuals can suffer from low, moderate or high risk factors that predispose them to schizophrenia. Therefore it could be stated that the dimensional model explains the range of schizophrenic illnesses better than the DSM provides.
There is also a divorce of aetiology and diagnostic criteria concerning schizophrenia within the DSM. Those who abide by the DSM approach to schizophrenia run the risk of rejecting empirical facts due to the DSM's lack of theoretical speculation regarding aetiology when forming diagnostic criteria. Without this association there can be no further research because of the absence of solid research. With this is in mind the current treatment options from the DSM do not include treating the specific cause or preventing the disorder before the onset of stated symptoms. It can be safely assumed that applying knowledge of schizophrenic aetiology would help develop better targeted treatments.
The DSM states psychosis as the core symptom and essential for the diagnosis of schizophrenia, however could this be a mistake? (Tsuaung et al., 2000). Evidence shows that psychosis is not exclusive to psychiatric disorders; it's also present in neurological diseases such as Alzheimer's or Parkinson's. The Schnedarian first-rank symptoms, widely recognized as the definitive criteria for forming schizophrenic diagnoses, occur in other psychotic disorders other than schizophrenia (Peralta et al., 1998). In fact, factor-analytic studies show that psychosis did not differ in schizophrenia and other disorders and types of psychopathology (Peralta et al., 1997). Therefore the DSM's focus on psychosis for diagnosing schizophrenia could be incorrect (Tsuaung et al., 2000). It should be noted however that these similarities between psychotic disorders don't necessarily suggest that the underlying disorders lie on the same continuum. It could be asserted that psychosis might hide more subtle differences between the disorders which could ultimately define them.
Schizotaxia refers to a body of research that builds a foundation on both the clinical and biological manifestations for the vulnerability of schizophrenia, introduced by Meehl to describe the predisposition of schizophrenia genetically (Meehl, 1962). As stated before genetic predisopstion is also influenced by environmental factors with Faraone and colleagues stating schizotaxia as way to describe the premorbid, neurological substrate of schizophrenia (Faraone et al., 2001). It has distinctive psychiatric and neurobiological features, including negative symptoms, neuropsychological impairment, deviant eye tracking, and structural brain abnormalities (Faraone et al., 2001). Schizotaxia signifies a more useful diagnostic criterion, with clinically significant condition and a potential risk factor for ensuing psychosis.
The growing evidence suggest that two diagnostic criteria for schizophrenia should be reconsidered