An American study has found a high level of agreement between the DSM IV definition of major depressive disorder (MDD) and a simpler definition which excludes the somatic criteria.

The simpler definition comprises the five psychological symptoms of depression:

• depressed mood
• loss of interest or pleasure
• worthlessness/guilt
• impaired concentration/indecision
• suicidal ideation

At least three symptoms must be present, one of which is low mood or loss of interest.

A total of 2,510 patients participated in the study: 1,100 were psychiatric outpatients, 210 were attending a gambling treatment programme and 1,200 were candidates for bariatric surgery. Patients were asked about all symptoms of depression using a single semistructured clinical interview, and DSM-IV and simplified MDD criteria were then applied.

For all three samples, a high level of agreement was found between the DSM IV and simplified MDD criteria

(κ >0.80). When the results for all 2,510 patients were combined, the two definitions were found to be in agreement 95.5% of the time. The simplified criteria did not agree with the DSM IV diagnosis of MDD in 64/564 patients (11.3%) and diagnosed MDD in 49/1,946 patients who did not meet the DSM IV criteria (2.5%).

The authors suggest that the simpler definition is preferable for two reasons. First, it is easier to remember and will reduce the time needed to make an assessment. Second, for patients with a chronic condition, it avoids the difficulty of deciding whether somatic symptoms are caused by depression or by the physical illness itself. Another group of patients for whom this is often a problem are antenatal and postnatal mothers.

However, this study is from secondary care, whereas in primary care somatic symptoms predominate.

In the WHO community study, 60% of the UK participants with major depression reported only somatic symptoms, and 40% of them had multiple medically unexplained somatic symptoms.¹

In the DEPRES II study, two of the three most frequently reported symptoms of depression were somatic (fatigue and sleep disturbance).² If we reduce awareness of somatic presentations of depression by excluding them from the definition of depression, it is likely that the proportion of patients with unrecognised depression will increase.

For patients with a chronic condition, the situation is more complex.

Recognition of depression may be facilitated by removing the uncertainty regarding somatic criteria. However, awareness of somatic presentations is even more important in these patients, who may present with a worsening of their physical condition, increased pain or reduced tolerance of physical symptoms.³

I think it would be a big mistake to adopt the simpler definition of MDD for everyone. Nevertheless, I think it can be a useful alternative for patients with somatic symptoms of uncertain genesis.