Is age of onset associated with severity, prognosis, and clinical features in bipolar disorder? A meta-analytic review

Objectives: To identify clinical characteristics and adverse outcomes associated with an earlier age of onset of bipolar disorder. Methods: A comprehensive search yielded 15 empirical papers comparing clinical presentation and outcomes in individuals with bipolar disorder grouped according to age of onset (total N=7370). The following variables were examined to determine odds ratios (ORs) and 95% confidence intervals (CIs): presence of Axis I comorbidity, rapid cycling, psychotic symptoms, mixed episodes (DSM-IV), lifetime suicide attempts, lifetime alcohol and substance abuse, symptom severity, and treatment delay. Results: Early age of onset was found to be associated with longer delay to treatment (Hedges' g=0.39, P=.001), greater severity of depression (Hedges' g=0.42, P<.001), and higher levels of comorbid anxiety (OR=2.34, P<.001) and substance use (OR=1.80, P<.001). Surprisingly, no association was found between early age of onset and clinical characteristics such as psychotic symptoms or mixed episodes as defined by DSM-IV. Conclusions: Earlier age of onset of bipolar disorder is associated with factors that can negatively impact long-term outcomes such as increased comorbidity. However, no association was found between early onset and indicators of severity or treatment resistance such as psychotic symptoms. Clinical features found to have the strongest relationship with early age of onset were those potentially amenable to pharmacological and psychological treatment. Results highlight the importance of early identification and provide potential areas of focus for the development of early intervention in bipolar disorder.