Prevalence and association of somatic symptoms in patients with Major Depressive Disorder

BACKGROUND: Painful and non-painful somatic symptoms are often reported in patients with depressive disorder. The proper identification of depression-relevant somatic symptoms is important for the accurate diagnosis of depression, development of treatment strategies and measurement of outcome. The objective of this study was to characterize the relationship between somatic symptoms and depression in patients diagnosed with Major Depressive Disorder (MDD), using data from randomized drug trials carried out by a pharmaceutical company. METHODS: Pooled 'blinded' data from 2191 patients enrolled in randomized, multicenter, double-blind placebo-controlled studies for the treatment of MDD were analyzed. Somatic symptoms were assessed using the Somatic Symptoms Inventory (SSI) and the Hamilton Depression Rating Scale (HAMD) was used to assess symptoms of depression. RESULTS: The most common somatic symptom reported by patients with MDD was 'feeling fatigued, weak, or tired all over', with 78% of patients reporting 'moderate' levels or above. This was followed by 'feeling that not in as good physical health as most of your friends' (59%), 'not feeling well most of the time in the past few years' (54%), and 'feeling weak in parts of body' (45%). 'Headache' was the most common pain-related symptom with 43% reporting 'moderate' or above. Pearson's product-moment correlations revealed that somatic symptoms generally increased as a function of overall depressive (r=0.43), with 'feeling fatigued, weak, or tired all over' (r=0.50), 'feeling that not in as good physical health as most of your friends' (r=0.42), 'feeling weak in parts of body' (r=0.41), 'heavy feeling in arms and legs' (r=0.34), 'not feeling well most of the time in the past few years' (r=0.32), and 'headache' (r=0.31) showing the strongest correlation with overall HAMD scores. Non-parametric item response analyses showed that many somatic symptoms demonstrate good relationship between item response and the overall severity of depression. In particular, 'feeling fatigued, weak, or tired all over' exhibited good discriminative properties across the full range of severity for depression. LIMITATIONS: The analysis utilized data from a 'restricted' patient population in drug trials sponsored by a pharmaceutical company. CONCLUSIONS: These results demonstrate a high prevalence and association of somatic symptoms in patients with MDD, including feelings of fatigue, physical malaise and pain-related symptoms, which could be potentially useful in the assessment of depression and in the evaluation of treatment strategies.