Effects of Dimensional and Categorical Classification on the Clinical Manifestation of Major Depressive Disorder

The aim of this study was to combine the dimensional concept with the categorical system in major depressive disorder (MDD) to reduce the complexity of the diagnosis. Furthermore, it was aimed to match categorical and dimensional approaches in a clear and simple manner.

The study included a patient group of 131 consecutive outpatients diagnosed with MDD according to the DSM-IV diagnosis criteria, and a control group of 99 people that is matched with the patient group by gender, age and education level. All subjects completed the Beck Depression Inventory, the Beck Anxiety Inventory and the Toronto Alexithymia Scale (TAS).

Cronbach's alpha values for the analysis of the internal consistency of the scale for the patients group, control group and the total participants were determined as .94-.97, .87-.92 and .93-.96, respectively. Nine factors were obtained from the results of exploratory factor analysis. According to the Scree-plot, it was decided that the two-factor structure represents best. Although depression and anxiety are two distinct dimensions, the relationship between them was found to be significantly significant. This was valid for both patient and control groups. When the relationship between the DSM-IV diagnosis criteria and all variables (depression and its sub-dimensions, anxiety and its sub-dimensions and the number of symptoms) was evaluated, the number of symptoms was found to be significantly related with all of the criteria.

The number of symptoms and the severity of illness are found to be important in the clinical manifestation of MDD. The relationship of the severity of the illness with sleep and appetite seems weaker. While loss of interest was mainly predicting the disorder, weight changes, psychomotor changes, difficulty in concentration, fatigue, and worthlessness were determined not to be predictors of the manifestations. According to dimensional approach, somatic anxiety and deterioration in performance predict the presence of the disorder. According to categorical and dimensional approaches, some of the DSM-IV criteria (#2, #1, #9, #4, number of symptoms, severity of symptoms, somatic anxiety, performance deterioration) are seen to contribute to the matchability between the approaches.