LEC 16: Bipolar disorder

What is bipolar disorder?

• involve either manic or hypomanic episodes plus major depressive episodes

• individuals often do not perceive that they are ill

Diagnostic features of bipolar 1

• A manic episode characterized by the following:

  • a. distinct period of abnormally elevated, expansive or irritable mood

  • b. three or more of the following:

    • more talkative

    • decreased need for sleep

    • flight of ideas/racing thoughts

  • c. causes marked impairment in social/occupational functioning

• A major depressive episode

Diagnostic features of bipolar 2

• A hypomanic episode characterized by the following:

  • a. distinct period of abnormally elevated, expansive or irritable mood

  • b. three or more of the same criteria as bipolar 1

  • c. episode is associated with an unequivocal change in functioning

  • d. disturbance in mood and change in functioning is observable by others

  • e. the episode is not severe enough to impair social/occupational functioning or result in hospitalization

• A major depressive episode

Prevalence of bipolar disorder

• male to female ratio is about 1:1

• bipolar 1: mean age of onset is 18

• bipolar 2: average age of onset is mid 20s

Etiology of bipolar disorder

• GWA studies reveal association of risk for bipolar with SYNE1, a gene which encodes nesprin-1

• nesprin-1 is crucial for proper positioning of the nucleus within the cell

• largely unknown however

Treatments for bipolar

First drug to somewhat successfully treat bipolar is Lithium, whose exact mechanism of action is unknown and is classifed as a ‘mood stabilizer’

Dopamine theory of bipolar (neurotransmitter dysfunction)

• based on observation that mania can be provoked in individuals who consume moderate to high does of amphetamines (which primarily work to elevate synaptic levels of dopamine)

• traditional drugs used to treat bipolar (Lithium, Valproate) do have some action on the D2/3 receptor

Brain-Derived Neurotrophic Factor (BNDF) theory of bipolar (cellular signaling)

• protein involved in plasticity of the brain

• if the brain is changing, BDNF is there to support new circuits/cell growth and promotes cell survival

• evidence that BDNF is decreased among patients with bipolar

Mitochondrial theory of bipolar (energy regulation)

• mitochondria are organelle responsible for multiple cellular functions (e.g. energy production)

• mitochondrial dysfunction impairs the brain’s energy supply, making neurons less resilient to stress and more prone to malfunction

• in bipolar, the mitochondria do not work well