Role of Age at Onset in the Clinical Presentation of Bipolar Disorder

There is considerable evidence to suggest that the clinical expression of Bipolar Disorder (BD) differs according to Age at Onset (AAO) that has therefore been identified as a potential specifier of interest. Aim: To compare the clinical presentation of BD and also to compare the presence of family history of illness in three subgroups made on the basis of AAO. Materials and Methods: A cross-sectional hospital based observational study was carried out on 162 patients having a diagnosis of BD current episode manic. Three subgroups were made according to AAO viz., Early Onset Bipolar Disorder (EOBD; AAO ≤21 years; 67 patients), Intermediate Onset Bipolar Disorder (IOBD; AAO=22-34 years; 59 patients) and Late Onset Bipolar Disorder (LOBD; AAO ≥35 years; 36 patients). The subgroups were compared on clinical variables, items of the Young Mania Rating Scale (YMRS), Hamilton Depression Rating Scale (HAM-D) and Scale for Assessment of Positive Symptoms (SAPS) scales and family history of illness. Results: The EOBD subgroup had significantly more episodes per year (p-value <0.001 and partial eta squared value=0.17) than IOBD and LOBD subgroups (mean episodes per year, respectively in EOBD, IOBD and LOBD were 1.8, 0.8 and 0.6). The prevalence of family history of mood disorder was also significantly higher in the EOBD (present in 35 out of 67; χ2 value=22.8 and p-value <0.001) than both the other subgroups (present in 10 out of 59 in IOBD and 6 out of 36 in LOBD). Significant differences were found on different items of YMRS, HAM-D and SAPS scales among the subgroups EOBD subgroup had higher rating on irritability, motor activity energy, sexual interest, depressed mood, delusions, thought disorders, while LOBD subgroup had higher rating on elevated mood. Conclusion: EOBD subgroup can be considered as a specific phenotype of BD patients, which is more homogenous, severe and heritable form of illness.