The overlap between the common mental disorders--challenges for classification.

It is argued that there are problems with psychiatric classifications with major mental disorders since there are no clear dividing lines between the psychoses, and these problems are compounded with common mental disorders. There are three possible solutions: hierarchical systems, postulating frequent 'co-morbidity' between many different syndromes, or adopting a dimensional approach. The advantages and disadvantages of each of these are discussed, but a pseudo-dimensional system might be the best solution at present. However, a well validated dimensional system should be possible at some future date.