Insomnia Associated with Depressive Disorder: Primary, Secondary, or Mixed?

BACKGROUND: Insomnia is a common problem that is known to occur during depression. However, literature still debates whether insomnia is part of depression or a separate entity. MATERIALS AND METHODS: Subjects presenting with depressive disorder according to DSM-IV-Text Revision criteria were recruited after seeking informed consent. Clinical interview was performed with the help of Mini International Neuropsychiatric Interview Plus. Their demographic data and depression related history were recorded. Depression severity was assessed by using Hamilton Rating Scale for Depression. Diagnosis of insomnia was made with the help of International Classification of Sleep Disorders-2 criteria. Type of insomnia, its duration, and its relationship with depressive illness were specifically asked. If any subject fulfilled criteria for more than one type of insomnia, both were recorded. Statistical analysis was done with the help of statistical package for social sciences (SPSS) version 17.0. χ(2) test, independent sample t test, and Pearson's correlation were performed. RESULTS: A total of 54 subjects were enrolled in this study. Primary insomnia was seen in 40.7% cases and secondary insomnia in 58.8% cases; 27.3% subjects did not experience insomnia along with depressive disorder. In the primary insomnia category, adjustment insomnia was most prevalent (63.6%), and in secondary insomnia group, insomnia due to depressive disorder was most frequent (59.3%). Interestingly, primary insomnia often followed an onset of depressive illness (P=0.04), while secondary insomnia preceded it (c(2) =11.1; P=0.004). The presence of either type of insomnias was not influenced by duration of depressive illness, number of depressive episodes, and duration of current depressive episode. On the other hand, duration of insomnia was positively correlated with total duration of depressive illness (P=0.003), number of episodes (P=0.04), and duration of current depressive episode (P<0.001). CONCLUSION: Primary insomnia is common in subjects with depression, and it usually follows depressive illness. On the other hand, secondary insomnia often precedes the onset of depressive illness. Duration of insomnia positively correlates with duration and frequency of depressive episodes.