Bipolar disorder is a chronic, episodic, progressive illness.1 Each episode substantially increases the risk that another will occur and will be less responsive to treatment than previous episodes, leading to a progressive degeneration in functionality, neurocognition, and quality of life, [McIntyre, 2011] and to an increased risk of suicide.2 Intervening prior to an episode (either the first episode, or an episodic relapse) can therefore mitigate disease progression.
One of the most significant impediments to first-episode prevention is the underdiagnosis of bipolar disorder.3 Since most patients initially present during a depressive episode, the disorder is frequently misdiagnosed as unipolar depression,4 resulting in a missed opportunity for appropriate intervention.
A second frequently missed “window” of early intervention involves relapse prevention. Bipolar disorder was once thought to consist of discrete episodes of mania or depression, with intervening periods of euthymia. But it is now understood that even during inter-episode periods, subsyndromal symptoms (e.g., emotional dysregulation, sleep and circadian rhythm disturbances, cognitive impairment, and increased risk for psychiatric and medical comorbidity) continue to exist,5 progressing to prodrome and increased relapse risk.
In their article “Is There a Clinical Prodrome of Bipolar Disorder: A Review of the Evidence,”6 Martin and Smith analyze the characteristics of bipolar prodrome, focusing on interventions at critical junctures so the prodrome does not develop into an acute episode.
Differentiating Between Unipolar and Bipolar Depression
Historically, unipolar and bipolar depression were regarded as identical. However, they may actually represent two distinct clinical entities.6 Unipolar depression tends to present with symptoms of excessive self-reproach, anergia, decreased libido, initial insomnia, weight loss, normal or low activity levels, somatic complaints, tendency to blame others, and anxiety. Bipolar depression, on the other hand, can present with psychotic features, diurnal mood variations, and hypersomnia. Additionally, individuals with BD may experience increased number and shorter duration of depressive episodes, abrupt onset and discontinuation, leaden paralysis, psychomotor retardation, lability of mood, and pathological guilt.6 There are also differences in memory and executive function: unipolar depression is characterized by impaired attention, mental processing speed, and mental flexibility, while bipolar disorder is characterized by deficits in sustained attention, verbal recall, memory, verbal fluency, and emotion-dependent cognitive processing. 6