Abstract
I am writing to address the contentious question of the classification of depression. The American Psychiatric Association's classification system takes a dimensional approach to the classification of depression. Essentially this creates a spectrum from mild to severe forms of depression with the assumption that a patient will move to some point along that dimension as they become more unwell and move back along that dimension as they recover. An alternative approach to the classification of depression is a category model in which the symptoms of the condition, or perhaps the type of depression, are on a separate axis to the severity of the condition. Consequently, a patient may have a mild to severe form of each category of depression but not necessarily the propensity to move from one category to another. I believe that this is important because the assumption that all forms of depression can be treated by different types of treatment, irrespective of the type of depression, can lead to an inappropriate treatment for a particular category.
In order to settle the issue it occurs to me that, if instances could be found where patients suffer a category of depression which may move from mild to severe but do not move through other categories of depression, this would argue strongly in favour of a category model as opposed to a dimensional model in which a patient might be expected to move from a mild form to a severe form and then reverse in recovery. It would be interesting if readers of this journal were able to produce case histories of patients who, for example, might suffer psychotic depression and go from being well into psychotic depression without necessarily proceeding through dysthymic or non-melancholic forms of depression and conversely, recover from this category of depression without moving along the dimensions. Similarly, readers may be able to identify patients who move straight into a melancholic form of depression and, likewise, revert out of the melancholic form without necessarily proceeding through other phases of the dimension. There are certainly individuals that I believe fulfil these criteria and if so, it would argue strongly in favour of the category form and consequently against a dimensional approach to the classification of depression.