2.6 Diagnosis - Anxiety or depression ?
As they have identified more and more people who may be "depressed", nosologists have helped to expand markets and sometimes create perfect niches for individual drugs. Alprazolam (Xanax, Upjohn) for "panic attacks" is a case in point. But what is the "depression market" and what does it reveal of "depression" itself ? In particular, are the diagnoses of "anxiety" and "depression" distinguishable ? To the extent they are not, it would have helped the SSRIs to get into the market previously dominated by the BDZs.
It is universally accepted that "anxiety" is a major part of "depression" but there is long-standing controversy about which is what. (Goldberg, 1995) Some believe they are variants of a single disorder; others hold they are distinct but overlapping entities. However, it would be generally agreed that most patients with depression can be diagnosed as anxious too, and that "major depression is a frequent secondary disorder associated with several of the anxiety disorders." (Keller & Hanks, 1995). Thus, DSM-IV includes a formal definition of "Mixed Anxiety-Depressive Disorder" and, in practice, antidepressants and anxiolytics (usually BDZs) are often used interchangeably or together at the same time. (Hale, 1997) Several well-controlled trials indicate that benzodiazepines tranquillisers are often as effective as antidepressants in treating "depression", just as antidepressants often work on "anxiety" too (Rickels et al., 1993).
Around 1960, the markets for anxiety and depression were much more as one: mainly barbiturates for anxiety and barbiturates+amphetamines for depression. The main concern would then have been to relieve the patients symptoms either by sedating or stimulating her - and being careful not to bring about a sudden swing of mood in either direction. (Both depression and anxiety are diagnosed twice as often in women than men).
With the simultaneous arrival of the first antidepressants and the BDZs, a stricter process of demarkation began. But this took time and uncertainty about the relationship between anxiety and depression is evident in some of the earliest assessments of the MAOIs:
"The question must now arise whether MAOIs are really the antidepressant drugs they are claimed to be or whether they act really more against anxiety, and perhaps as stabilisers of the autonomic nervous system. Such a question inevitably brings up the controversial problem of what is meant by the terms depression and anxiety. Lewis (1934) believes that it is impossible to separate clinically groups of depressions one from the other; he regards anxiety often as a symptom of depression, and anxiety states and depression as forming one long continuum of illness". (Sargant & Dally, 1962)
"These findings suggest that the beneficial effect of phenelzine (an MAOI) in depressive illness is due more to a sedative action in relieving anxiety than to a specific antidepressant action." (Hare et al., 1962)
The overlap between anxiety and depression is also prominent in an important diagnostic tool, the Hamilton Rating Scale for Depression. (Hamilton, 1967). This scale, still the most widely used to screen patients entering clinical trials, includes many questions about anxiety. As a result "an effective anxiolytic agent may substantially reduce total scores and such reductions are then often uncritically interpreted as evidence of antidepressant efficacy" (Healy, 1991). The same writer has also noted that "Hamilton himself did not see his scale as an instrument for measuring the severity of changes in a depressive illness. Rather he saw it initially as a checklist of questions clinicians should be asking and observations they should be making. A great number of these questions and observations concern anxiety." (Healy, 1990)
Neither is the distinction between depression and anxiety too clear from long dominant theories about the biological basis of depression, and the role of serotonin (5-HT). Though specifically identified as one of the keys to depression, serotonin is closely linked to "anxiety" too.
" ... a great number of new compounds, with relatively specific actions on the 5-HT system ... have begun to appear on the market. Are they anxiolytic or antidepressant or both ? The overview, above, of the behavioural effects mediated through 5-HT receptors suggests that 5-HT has more to do with anxiety than depression. This however, is an issue that is likely to be confounded greatly by the efforts of drug companies to market their products" (Healy, 1991).
The evidence suggests some repositioning of "anxiety" through the promotion of "depression", over most of the last ten years. Anxiety is now on the back-burner and depression has become the dominant "disease". Then we were anxious, now we are depressed. Valium out, Prozac in.
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