Variability of clinical picture

Abstract

Psychiatric diagnostic constructs produce highly variable clinical pictures in patients. Amongst the reasons for this are high rates of co-occurrence of different diagnostic constructs, which themselves are often polythetic in nature. People who meet criteria for a diagnostic construct may have little or even no clinical features in common. These diagnostic constructs rely on people meeting the diagnostic criteria having similar qualities to their condition such as similar likelihoods of outcomes/responses to treatments. These highly variable clinical pictures are seen even when clear disease is involved, such as the dementias. General medical diagnostic constructs can also display highly variable clinical pictures even when clear disease processes have been identified. Polythetic diagnostic criteria decided upon by expert committees are also used for general medical diagnostic constructs which can also result in people meeting the same diagnostic criteria having little in common in their clinical pictures. Co-occurrence is also common in general medicine. Psychological formulation does not have to address the issue of variable clinical pictures. Both symptom-based and dimensional classifications can depict variable clinical pictures more accurately than diagnostic constructs but there are pragmatic issues such as suitability for brief appointments or emergency work.