Somatic symptoms: an important index in predicting the outcome of depression at six-month and two-year follow-up points among outpatients with major depressive disorder.

BACKGROUND

Few studies have simultaneously compared the ability of depression, anxiety, and somatic symptoms to predict the outcome of major depressive disorder (MDD). This study aimed to compare the MDD outcome predictive ability of depression, anxiety, and somatic severity at 6-month and 2-year follow-ups.

METHODS

One-hundred and thirty-five outpatients (men/women=34/101) with MDD were enrolled. Depression and anxiety were evaluated by the Hamilton Depression Rating Scale, Hospital Anxiety and Depression Scale, and depression subscale of the Depression and Somatic Symptoms Scale (DSSS). Somatic severity was evaluated by the somatic subscale of the DSSS. Subjects undergoing pharmacotherapy in the follow-up month were categorized into the treatment group; the others were categorized into the no-treatment group. Multiple linear regressions were used to identify the scales most powerful in predicting MDD outcome.

RESULTS

Among the 135 subjects, 119 and 106 completed the 6-month and 2-year follow-ups, respectively. Somatic severity at baseline was correlated with the outcomes of the three scales at the two follow-ups. After controlling for demographic variables, somatic severity independently predicted most outcomes of the three scales at the two follow-ups in the no-treatment group and the cost of pharmacotherapy and DSSS score at the 6-month follow-up in the treatment group.

LIMITATIONS

Division of the subjects into treatment and no-treatment groups was not based on randomization and bias might have been introduced.

CONCLUSIONS

Somatic severity was the most powerful index in predicting MDD outcome. Psychometric scales with appropriate somatic symptom items may be more accurate in predicting MDD outcome.