Spectrum disorder

A spectrum disorder is a mental disorder that includes a range of linked conditions, sometimes also extending to include singular symptoms and traits. The different elements of a spectrum either have a similar appearance or are thought to be caused by the same underlying mechanism. In either case, a spectrum approach is taken because there appears to be 'not a unitary disorder but rather a syndrome composed of subgroups'. The spectrum may represent a range of severity, comprising relatively 'severe' mental disorders through to relatively 'mild and nonclinical deficits'. A spectrum disorder is a mental disorder that includes a range of linked conditions, sometimes also extending to include singular symptoms and traits. The different elements of a spectrum either have a similar appearance or are thought to be caused by the same underlying mechanism. In either case, a spectrum approach is taken because there appears to be 'not a unitary disorder but rather a syndrome composed of subgroups'. The spectrum may represent a range of severity, comprising relatively 'severe' mental disorders through to relatively 'mild and nonclinical deficits'. In some cases, a spectrum approach joins together conditions that were previously considered separately. A notable example of this trend is the autism spectrum, where conditions on this spectrum may now all be referred to as autism spectrum disorders. In other cases, what was treated as a single disorder comes to be seen (or seen once again) as comprising a range of types, a notable example being the bipolar spectrum. A spectrum approach may also expand the type or the severity of issues which are included, which may lessen the gap with other diagnoses or with what is considered 'normal'. Proponents of this approach argue that it is in line with evidence of gradations in the type or severity of symptoms in the general population. The term spectrum was originally used in physics to indicate an apparent qualitative distinction arising from a quantitative continuum (i.e. a series of distinct colors experienced when a beam of white light is dispersed by a prism according to wavelength). Isaac Newton first used the word spectrum (Latin for 'appearance' or 'apparition') in print in 1671, in describing his experiments in optics. The term was first used by analogy in psychiatry with a slightly different connotation, to identify a group of conditions that is qualitatively distinct in appearance but believed to be related from an underlying pathogenic point of view. It has been noted that for clinicians trained after the publication of DSM-III (1980), the spectrum concept in psychiatry may be relatively new, but that it has a long and distinguished history that dates back to Emil Kraepelin and beyond. A dimensional concept was proposed by Ernst Kretschmer in 1921 for schizophrenia (schizothymic – schizoid – schizophrenic) and for affective disorders (cyclothymic temperament – cycloid 'psychopathy' – manic-depressive disorder), as well as by Eugen Bleuler in 1922. The term 'spectrum' was first used in psychiatry in 1968 in regard to a postulated schizophrenia spectrum, at that time meaning a linking together of what were then called 'schizoid personalities', in people diagnosed with schizophrenia and their genetic relatives (see Seymour S. Kety). For different investigators, the hypothetical common disease-causing link has been of a different nature. A spectrum approach generally overlays or extends a categorical approach, which today is most associated with the Diagnostic and Statistical Manual of Mental Disorders (DSM) and International Statistical Classification of Diseases and Related Health Problems (ICD). In these diagnostic guides, disorders are considered present if there is a certain combination and number of symptoms. Gradations of present versus absent are not allowed, although there may be subtypes of severity within a category. The categories are also polythetic, because a constellation of symptoms is laid out and different patterns of them can qualify for the same diagnosis. These categories are aids important for us practical purposes such as providing specific labels to facilitate payments for mental health professionals. They have been described as clearly worded, with observable criteria, and therefore an advance over some previous models for research purposes. A spectrum approach sometimes starts with the nuclear, classic DSM diagnostic criteria for a disorder (or may join together several disorders), and then include an additional broad range of issues such as temperaments or traits, lifestyle, behavioral patterns, and personality characteristics. In addition, the term 'spectrum' may be used interchangeably with continuum, although the latter goes further in suggesting a direct straight line with no significant discontinuities. Under some continuum models, there are no set types or categories at all, only different dimensions along which everyone varies (hence a dimensional approach). An example can be found in personality or temperament models. For example, a model that was derived from linguistic expressions of individual differences is subdivided into the Big Five personality traits, where everyone can be assigned a score along each of the five dimensions. This is by contrast to models of 'personality types' or temperament, where some have a certain type and some do not. Similarly, in the classification of mental disorders, a dimensional approach, which is being considered for the DSM-V, would involve everyone having a score on personality trait measures. A categorical approach would only look for the presence or absence of certain clusters of symptoms, perhaps with some cut-off points for severity for some symptoms only, and as a result diagnose some people with personality disorders.