Introduction
Psychologists, clinicians, and other health experts have had a lengthy debate on whether dimensional approaches ought to be included in the DSM-V or not. Currently, it appears that the proposal to include the dimensional assessments together with the existing categorical diagnosis in the DSM-5 manual is gaining a great momentum.
First, Frances, and Pincus (2004) argue that this move is expected to ease the manner in which treatment is administered and monitored. The inclusion of dimensional approaches to disorders such as schizophrenia in the DSM-V will provide additional information to psychologists and clinicians in the diagnosis and treatment of various psychological conditions.
The dimensional approach to schizophrenia is quite important before the actual diagnostic evaluation is carried out. Some of the prior dimensional assessments include evaluation of depression in primary care and identification of features that are related to suicidal ideation.
The inclusion of this approach in the DSM-V may also lead to a transition that may see the current DMS change from paper-based self-report questionnaires to a system that is fully computerised (Praag, Kloet, & Os, 2004).
Although there a couple of advantages associated with the inclusion, the dimensional approaches have a number of shortfalls. The most pronounced disadvantage arises from the statistical components of the dimensional approach, which may complicate its use (Stein & Wilkinson, 2007).
It is evident that the inclusion of dimensional assessments with the existing categorical diagnoses in DMS-5 has both advantages and disadvantages. Recommendations as to whether or not it would be prudent for the DSM-5 to include the dimensional assessments in the existing system should be based on the pros and cons of this inclusion.
Schizophrenia and the Dimensional Approach
Schizophrenia is a psychiatric condition, which is characterised by a persistent, in most cases chronic, mental illness. The condition is known to affect thinking, behaviour, and emotion. Schizophrenia is often characterised by positive symptoms linked to normal experiences and behaviour and negative symptoms that show a decline in normal practices and character (Tsuang, 2011).
The positive symptoms include hallucinations, thought disorder, and delusions while the negative ones consist of mannerisms such as lack of or inappropriate emotion, lack of passion, and poor development of speech (DeLisi, 2011).
It is important to point out that the psychiatrists are still yet to come up with the definite causes of schizophrenia. However, most medical practitioners and researchers who specialise in psychosomatic disorders assert that Schizophrenia is a condition of the brain. For that reason, the disorder is linked to a mixture of factors, but the main ones include hereditary disposition and environmental stress (Taylor, 2006).
Shean (2004) argues that genetic studies that have been conducted show that family of people with schizophrenia have higher chances of suffering from the disorder in their lives than those from non-schizophrenic families.
The dimensional approach to schizophrenia works hand in hand with relevant statistical procedures to identify the most pronounced group of symptoms that are known to occur together. However, this does not apply to the symptoms that occur by chance, in an exclusive manner. In fact, it is these empirically derived symptoms that are referred to as dimensions (Praag, Kloet, & Os, 2004).
In the 1980s, the researchers of this brain disorder were able to make a breakthrough. They discovered the existence of three syndromes in the diagnostic category of this disorder. In this category, both the negative and positive symptoms’ dimensions were more replicated across the studies that are more recent than the others (Praag, Kloet, & Os, 2004).
The dimensional approach functions differently from other approaches to schizophrenia. The dimensional approach allows for the allocation of each individual through the use of the same statistical procedure. The dimensional system is also flexible since the same individual can obtain any level of score on any of the dimensions that are featured.
For instance, if there are two dimensions of negative and positive symptoms, some people may record high scores on both, some on only one of the two, while others may fail to score anything on both of the dimensions (Ritsner, 2010).
The dimensional approach is considered the best system, especially for research purposes. Firstly, the approach has clinical validity due to the fact that psychopathology is accorded a quantitative expression as opposed to a qualitative one. As a result, each individual is able to get a unique mix of scores on different symptom dimensions that in turn give the most accurate picture in clinical practice (Leigh, 2010).
Since the main aim of the dimensional approach is to examine psychopathology heterogeneity and other mechanisms linked to it, it becomes advantageous to express this attribute in terms of the symptoms themselves as opposed to clusters of individuals. However, due to the complicated statistical procedures associated with the dimensional approach, it is not considered as the most suitable system for clinical practices (Johannessen, 2006).
Why Dimensional Approaches Should Be Included in the DSM-V
There are many reasons supporting the inclusion of dimensional diagnosis of schizophrenia in the DSM-V. Firstly, schizophrenia like many other disorders is an indication that there is something wrong with an individual and that he or she requires a diagnosis, which refers to the expert’s intervention to reveal whether or not the disorder is present.
Therefore, the choice of using a dimensional system as opposed to a categorical one does not only depend on the nature of the disorder, but also the quality of the diagnosis (Oldham, Skodol, & Bender, 2009).
A dimensional approach has at least three ordinal values, which makes it easy for an individual to have more than one score in the measuring scales. The ordinal values vary from a 3-point scale to a continuum and this makes the dimensional approach better than the categorical one, which only contains two possible values: present and absent.
As a result, it is easier to transform each dimensional diagnosis into a categorical system by simply setting a cut point. Although there are still no distinct advantages of using the dimensional approach instead of categorical one, some studies show that the dimensional diagnosis detects the treatment effects of schizophrenia better than the categorical one.
The dimensional approach also has less attenuation as a result of its great accuracy in size estimation (Stricker, Widiger, & Weiner, 2003).
The dimensional approach is transparent to clinic practitioners and has greater clinical validity. The approach also has test-retest reliability for most of the mental disorders, especially schizophrenia.
Although the actual test that included both dimensional and categorical diagnosis did not give any statistical difference in the two systems, the most important thing is that a dimensional approach has more options than its categorical counterpart.
The dimensional approach is actually needed to make it possible for the inclusion of biochemical features, imaging and more so, the genetic elements that relate to schizophrenia (Janicak, Marder, & Pavuluri, 2011).
The inclusion of the dimensional diagnosis of schizophrenia and other disorders to DSM-V will help to avoid some of the problems that are currently faced by the system.
Some of the problems that are common with using the categorical approach alone include the inability to predict the components of the disorders independently, disappearance of data as a result of using the dichotomous variables to detect each component of the disorder, and the difficulty in using this intervention in individuals with different lifestyles (Kearney & Trull, 2012).
The inclusion of the dimensional approach will not only eliminate these problems, but also add some advantages to the DSM-V. The dimensional diagnosis is easier to use since it does not apply the multivariate predicting equations; it has a way of encouraging clinicians to look for multiple risk factors in patients. Additionally, Yip (2007) argues that dimensional diagnosis has the tendency to promote behavioural diagnosis as opposed to individual risk factors.
When the dimensional approach is included in the DSM-V construct, the clinicians will be able to design the construct so as to measure other characteristics that it didn’t gauge before. For instance, some of the characteristics that could be measured after its inclusion include family history and any other features of putative diagnostics that the medics will deem valuable.
This will be possible since the dimensional approach allows for the creation of a diagnostic scale comprising of dimensional items such as latent trait modelling, factor analysis, and item response theory among others (Ritsner, 2011).
Since the DSM’s categorical approach has proven incapable of accounting for the multiple sources of variance, the only way to get this accountability is by incorporating the dimensional approach into the system.
Several studies of child psychopathology, which have been conducted over the past two decades, have applied dimensional approaches in the clinical samples. The dimensional measures of adolescent psychopathology have become so common that they are now forming part of teaching and paediatric practices (Smith, Conway, & Cole, 2009).
The incorporation of the dimensional approach into the DSM system makes it easy for it to assess weaknesses inherent in a one-size-fits-all system. A diagnosis using the dimensional system also helps to identify variances that are caused by differences in age and gender.
Since the dimensional approaches have the ability to account for the multiple sources of variance, it is certain that their inclusion into the DSM-V system will bring advancement in evidence-based psychiatry (First, Kupfer, & Regier, 2002).
The current DSM’s categorical approach cannot quantify the neuro-scientific explanations of psychopathology. It is sometimes important to provide enough quantities to back up such explanations for a better understanding of the process.
At present, dimensional approaches are required to account for diverse neural circuits and other genes that play crucial roles in the psychopathology. The only way that this can be made possible is by including the dimensional approach to the DSM system (Stricker, Widiger, & Weiner, 2003).
The quantification of the expressions is needed since the connections, anatomy, and physiology of the human brain is known to have a dramatic change all through the various stages of development. In this regard, applying the current system exclusively without the inclusion of the dimensional approaches renders the system weak and unreliable.
For instance, the current categorical approach is not useful in a situation where genetic aspects of psychopathology portray continuous links with psychopathologic behaviours since it has weaker statistical power (First, Kupfer, & Regier, 2002).
Schizophrenia is regarded as a brain disorder and it falls under the brain imaging document, which normally overlaps among the DSM categories. Consequently, some genes and neural factors could present vulnerability to other conditions that are grouped under different DSM groupings.
For instance, when considering the amygdale’s size and function, it becomes easier to understand how the size and the function vary with one’s age, genetic disposition and gender (Smith, Conway, & Cole, 2009).
A good diagnostic system is one that allows for genetic and neural variations. This way, the system is able to cope with neuro-scientific advances. The most appropriate way to enable the DSM-V system to accommodate such advancements is including the dimensional approach in it. As a result, the system will automatically account for all the variances that are related to age, genetic disposition, and gender.
A high degree of relation between the changes in prefrontal cortical structure and the functions that are related to variations in psychiatric symptoms, over a given period of time, will also be easy to achieve (Stricker, Widiger, & Weiner, 2003).
When the dimensional approach is incorporated into the DMS-V system, there will be a full control of the sources of variance that have not been considered. Some of the sources that have been ignored in the current DMS system include gender, co-morbidity, age, and informants (First, Kupfer, & Regier, 2002).
The manual that is in use cannot account for the gender disproportion in infancy and its cutback in later life. First, Kupfer, and Regier (2002) argue that at least three times more boys than girls achieve the minimum requirement for the DSM diagnostic procedure for schizophrenia. This is not the case in adulthood in which as many women as men achieve this threshold.
Dimensional diagnosis and its statistical approaches provide systematic methods for proper selection of gender sensitive cut-offs and this helps in correcting the variance caused by gender (Smith, Conway, & Cole, 2009).
The dimensional approach also helps to correct the variance caused by co-morbidity. There have been situations where progeny do qualify in DSM procedure for schizophrenia and other disorders. These children are said to have multiple disorders which occur simultaneously (Stricker, Widiger, & Weiner, 2003).
The current DSM system does not give any proper reference to these children who experience numerous mental disorders simultaneously. However, this situation can be rectified by using a system that is capable of assessing higher order patters based on co-morbidity among separate disorders. It is only through the dimensional approach that such a system can be erected (Helzer, Kraemer, & Krueger, 2009).
Attributes such as age and the informant are other sources of variance that the current DSM’s categorical approach does not take into consideration. The approach is weak when used in the evaluation of 2, 12, 32, and 42-year-old patients suffering from schizophrenia (Helzer, Kraemer, & Krueger, 2009).
The procedure involving the dimensional diagnosis can be used by clinicians in understanding the developmental continuities that are related to antagonistic dimensions, which may be experienced by children. As a result, this approach explains exclusively how the adolescents may acquire an adult disorder.
Informants, on the other hand, come up as a result of the incapability of the categorical approach to successfully incorporate disparate data into the diagnostic process involved in schizophrenia. Since the dimensional approach has normative data, it can handle informant variance in an excellent manner (Lieberman, 2006).
Inclusion of dimensional approaches will also assist in combating other disorders such as those that stem from anxiety. The inclusion will lead to incorporation of a greater amount of potentially relevant information and make the DSM system stable for long. The system will also end up with a better predictive and discriminating power accompanied by higher levels of reliability.
Since the dimensional instruments are available for a variety of domains, the approach will be universal and is likely to be accepted by clinicians and researchers (Tamminga, Sirovatka, & Regier, 2010).
The inclusion of the dimensional approaches into the DSM-V system may help in solving the problem of wording that is associated with the use of categories. The use of the current DSM’s categorical approach normally results in huge alterations in analytical concordance for small wording differences.
It is through the inclusion that such effect can be neutralised. The dimensional approaches have statistical components that can be used to counteract the effect of the wording problem (Regier, Narrow, & Kuhl, 2011).
Lastly, dimensional approach is quite important in the assessment of co-occurring depressive and anxiety symptoms. The inclusion of the dimensional approaches in DSM-V will assist in eradicating the problem of the continuously disseminated phenomena that normally results from categorised diagnosis.
The dimensional approach not only describes the co-occurrence of the two disorders but also helps in the prediction of the impact that might result from such co-occurrence (Helzer, Kraemer, & Krueger, 2009).
Reasons Against the Inclusion
Although the inclusion of dimensional approaches would certainly make the DSM-V system superior and more flexible, the inclusion has a number of shortcomings as well.
Firstly, the dimensional approach is complicated in nature due to the statistical procedures that are involved in it (Million, Krueger, & Simonsen, 2010). The dimensional procedure is very complicated and it requires rigorous training of the clinicians and the researchers who plan to use the procedure (Engler, 2009).
Another limitation of the dimensional approach to schizophrenia is the limited scope of its self-report scales. It is difficult to use these scales in determining duration and persistence. The situation is even worsened further by the scales almost exclusive focus on the current state (Salloum & Mezzich, 2009).
It is recommended that the diagnosis takes the shortest time possible, but with these conditions, the dimensional approach could prolong the process and affect the time of treatment (Mash & Wolfe, 2010).
Lastly, the lumping together of schizophrenia, based solely on factor analytic approaches or dimensional diagnostic data, appears to be of restricted value.
The problem with this limitation is that it is difficult for the clinicians and other users of the new DSM-5 to obtain a clear structure of the disorder. These restrictions would make it difficult to understand the disorder and its treatment prescription (Aneshensel & Phelan, 2006).
Conclusion
It is clear that the inclusion of the dimensional approaches with the current DSM’s categorical diagnosis will certainly make the system stronger and more reliable. The dimensional approach has a number of benefits to clinicians, patients, and even the researchers, since it allows for flexibility in diagnosis on either the primary symptom level or the higher-order factor level.
As a result, it is easier to organise psychotherapeutic interventions around scenarios and recurrent themes, and correction of coverage problems in the DSM system.
The only serious limitation of dimensional approach is its statistical component, which can be easily dealt with. It would be prudent to include dimensional considerations of mental disorders in the next revision of the DSM manual that is due for release in 2013.
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