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Bipolar Affective Disorder: Epidemiology

  • According to WHO, Depressive disorder is the 4th & Bipolar disorder is the 6th leading cause of disease burden.
  • Depressive disorder & Bipolar disorder hold large similarities in pathogenesis, course of illness & outcomes. It is estimated that approximately 1% of patients convert from unipolar depressive disorder to bipolar disorder per year.


  • Bipolar I Disorder = about 1% (Females = Males)
  • Bipolar II Disorder = about 1.1% (Females > Males)
  • Bipolar disorder is seen more common in Divorced, Single persons & Upper socioeconomic groups.

Onset & Course

  • Mean Age of Onset = 17-30 years
  • In Bipolar I Disorder, majority of patients have depression as 1st episode. Approximately 85% patients have depressive, 10% have manic & 3- 5% have mixed episode as 1st episode.
  • About 80% of affective episodes are of depressive type & 20% manic or mixed types.
  • Typical Duration of depressive episode = 2- 5 months
  • Typical Duration of manic episode = 2 months
  • Risk of recurrence increases with the number of prior affective episodes.
  • Bipolar disorder patients suffer from affective symptoms of some severity approximately half of their lifetime.

Risk Factors for Bipolar Disorder

1. Genetic Factors:

Bipolar disorder is one of the psychiatric disorder with the highest heritability (about 70-80%).

2. Environmental Factors:

(i) Post-Partum:

Many women have their 1st episode of depression or mania in the post partum period.

(ii) Seasonal:

Manic episodes occur more commonly in late spring & early summer.

(iv) Circadian Rhythm:

Disruption of circadian rhythm through shift work or other factors which disrupt the normal sleep cycle may be important trigger to the onset of episodes of mania or depressive episode.

(v) Life Events:

Adverse life events may precipitate manic/ depressive episodes. Life events are more likely prior to the 1st or 2nd episodes of mania & are less likely later in the course of illness.


The most common comorbid disorders are:

  1. Anxiety Disorders
  2. Alcohol or Drug dependence
  3. Antisocial Behaviours

Social, Functional & Cognitive Outcomes

  • Approximately 60% of patients complain persistent cognitive deficits.
  • Approximately 2/3rd of patients are unable to regain premorbid levels of social & vocational functioning following a single episode.
  • They have 2-3 times increased risk of dementia in the long-run & risk of dementia may increase with the number of episodes. Long–term treatment with Lithium (mood stabilizer) may decrease the risk of dementia.
  • About 20-40% bipolar patients are misdiagnosed as unipolar depressive disorder. Treatment with antodepressants may further worsen the longitudinal course of bipolar disorder, principally by causing more switching or more mixed states.
  • There is often an interval of about 8-10 years of mood episode & seeking psychiatric help. Delay in Diagnosis has been considered as major contributor to poor outcome in Bipolar Disorder. Undiagnosed/ untreated patients suffer problems in relationships, employment, finances & health. Delay in diagnosing Bipolar Disorder increases the risk of suicide and also lead to longer hospitalization period.


  • Standardized mortality rates in Bipolar disorder is increased 2-3 times.
  • Life expectancy has been reported to be decreased by 8-12 years for patients with Bipolar disorder.
  • Causes for increased mortality: Suicide, unintentional injuries, comorbid general medical conditions (Diabetes, COPD & cardiovascular disease).
  • Reasons for increased mortality due to comorbid general medical conditions: Unhealthy lifestyle, Decreased health care, adverse pharmacological effects & biological factors.


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