The heterogeneity of “major depression”

Abstract

The concept of major depression, in both the ICD and the DSM, has been a flagship for mental health in general medical settings. It is the principal mental disorder emphasized to general practitioners and hospital doctors, and it has been used by governments to raise awareness of mental health issues in the population at large and in the medical community 1,2,3. It has encouraged the development of specialized forms of psychotherapy for depression, it has allowed the formation of community groups to propagate accurate information about depression, and has led to the development of computer programmes to assist self-treatment using the principles of cognitive-behavioural therapy 4,5. These are substantial achievements, but they come at a price. This is the belief that “major depression” is a homogeneous entity, and indeed that it is usually a “major” disorder. The DSM diagnosis of major depression is made when a patient has any 5 out of 9 symptoms, several of which are opposites. Thus, a patient who has psychomotor retardation, hypersomnia and gaining weight is scored as having identical symptoms as another who is agitated, sleeping badly and has weight loss. This causes real problems with research designs: for example, Lux and Kendler 6 had to group these opposite symptoms together. Even so, it was possible for them to distinguish between “cognitive” and “neurovegetative” symptoms, and show that these have different relationships to a larger set of potential validators. They concluded that their results “challenge our understanding of major depression as a homogeneous categorical entity”. Others have been able to separate the various depressive symptoms, and to compare the relative efficiency of each symptom to making the diagnosis 7. Jang et al 8 factor analysed a larger set of depressive symptom scales, and found that they could identify 14 different subscales, which had rather low intercorrelations, and very different heritabilities. Given these findings, to declare that all those satisfying the DSM criteria for the diagnosis of major depression are suffering from the same disorder seems like magical thinking. We know that many milder cases remit without specific treatment, suggesting that they are indeed homeostatic responses to life stress 9. Depression may be a toxic reaction to drugs or may result from endocrine disorders such as myxoedema or Cushing's syndrome. The depressed phase of bipolar illness may be difficult or impossible to distinguish from unipolar depression. Melancholic, atypical and psychotic forms of depression are yet other variants. Agitated depression needs to be distinguished from retarded depression when choosing the most suitable antidepressant. But even with these exclusions, there are five other forms of major depression that require a range of different responses from the clinician. The first form is depression presenting with somatic symptoms 10. Many patients with this condition may be resistant to accepting that they are depressed. They benefit from special additional measures that explain how emotional arousal and depression can cause their somatic symptoms. Such measures have been developed for many years, and have recently been elaborated 11. The second form is depression with panic attacks. While treatment of depression is the first priority in these patients, it is also important to give them advice on what to do during a panic attack, as it may take a little time before improvement in their depression stops further attacks. They need advice about not immediately leaving the environment in which the panic attack is taking place, explanations about catastrophizing thoughts and advice on helpful “self-talk”. They need to remind themselves that they have had such attacks before, and they will pass off if they calm down and remember the reassuring thoughts that run counter to the content of their thoughts during an attack. Such advice makes the attacks easier to deal with, and less likely to become still worse. The third form is depression in people with obsessional traits. People with these traits in their usual personality often develop quite severe obsessional behaviour and depressive ruminations during a depression. These symptoms may be experienced as the leading symptoms, but can be thought of as epiphenomena of their depressive illness. It is helpful to take the patient through thought-stopping techniques, distraction techniques and response prevention. The fourth form is depression accompanying known physical illnesses. These depressions are particularly poorly recognized by generalists, who typically confine themselves to the treatments for the physical illness 12. Diagnosis of these depressions is complicated by the fact that four of the “diagnostic features” of depression (fatigue, poor sleep, poor appetite and weight loss) may well be caused by the physical illness. This may generate confusion, since no clear threshold for the number of symptoms needed for a di