Tyrer's (2001) perspicacious editorial argues cogently for the recognition of a syndromal diagnosis of mixed anxiety and depression, collating supportive evidence from various fields of study. A ‘combined anxiety and depressive disorder’ model that extends beyond ICD-10's (World Health Organization, 1992) sub-syndromal mixed anxiety and depressive disorder (MADD), in terms of severity, seems to be a reasonable proposition and one that clearly has salience in terms of classification, epidemiology, clinical practice and treatment. To denote this ‘distinct syndrome’ the author resurrects the term cothymia, explaining that it represents ‘two moods of equal significance occurring together’ and that it perhaps provides the desired diagnostic differentiation.
However, the diagnosis of MADD was created to better understand the emergence of anxiety and depressive disorders and to determine whether the two groups of disorders arise from a common pool of biological abnormalities or whether mixed presentations reflect the overlap of essentially separate pathologies. This has clearly not yet been achieved and the assignment of a ‘diagnosis’ is perhaps somewhat premature. Indeed, Tyrer notes the significant degree of association between anxiety and depression and suggests that this does not invalidate separate or comorbid disorders. A DSM-IV Task Force (Frances et al, 1992) suggested four models for associations between anxiety and depression: (a) distinct but sometimes coexistent syndromes; (b) symptoms of anxiety and depression denoting similar external manifestations of a single underlying cause; (c) anxiety predisposing to depression; and (d) the converse, depression predisposing to anxiety. Tyrer (2001) asserts that the term cothymia ‘implies that anxiety and depression are equal partners in its presentation’, a message that, while clear, may not be completely accurate (Malhi et al, 2002). In terms of pathogenesis, several studies have demonstrated that, in practice, anxiety most often precedes depression (model 3) and that it probably plays an important role in its aetiology (Breslau et al, 1995; Parker et al, 1999). Furthermore, comorbid anxiety and depression show considerable variation clinically, and thus for the purposes of diagnosis and management it is perhaps more useful to retain recognition of their discrete contributions.
It is evident that greater clarity is urgently required with respect to the classification of anxiety and depressive disorders. To this end, the editorial is a welcome re-evaluation of a common diagnostic problem and may generate the necessary impetus for further investigation and research.
EDITED BY MATTHEW HOTOPF