Study of prodromal and residual symptoms of depression

The definitive diagnosis of depression calls for fulfillment of certain criteria in terms of symptoms, severity, and duration, but subthreshold cases are not uncommon. These may evolve to become clinically diagnosable depression preceded by prodrome. The current study was conducted to study prodromal and residual symptoms in depression.

Eighty follow-up patients of depressive episode (F32, International Classification of Diseases-10) in remission defined by Hamilton Depression Rating Scale score <8 were interviewed. A symptom was identified as prodromal if it appeared at any time before the period of onset of symptoms sufficient to fulfill the criteria to make a diagnosis of depressive episode. Clinical Interview for Depression and Related Syndromes was used to identify the presence of symptoms. Statistical analysis was done with McNemar test and Pearson's Chi-square test using SPSS software version 20.0.

The mean age of patients was 41.25 (±8.58) years and the sample was predominately female patients (80%). All the eighty patients had at least one prodromal symptom. The mean duration of prodrome was 115 (±64.46) days. Irritability (45%), insomnia (45%), and reduced energy (43.8%) were the most frequent prodromal symptoms. Frequency of irritability was comparable in prodromal and residual phases of depression (P = 0.074) and significantly associated with a positive family history of depression (P = 0.004).

Prodrome is present in most cases of depression lasting from weeks to months. Prodrome is frequented by irritability, anxiety, sleep problems, and fatigability. Irritability is associated with genetic loading of depression and likely to present as residual symptom if it is present in prodromal phase.