Causes

The causes of bipolar disorder are not fully understood, but genetic factors

play a major role. Approximately 80 percent of individuals with bipolar disorder

have a relative with some form of mood disorder, whether bipolar disorder

or depression. It is not uncommon to see families in which several

generations are affected by bipolar disorder. Serotonin, norepinephrine,

generations are affected by bipolar disorder. Serotonin, norepinephrine,

and dopamine, brain chemicals known as neurotransmitters that regulate

mood, arousal, and energy, respectively, may be altered in bipolar disorder.

A diathesis-stress model has been proposed for some psychosomatic disorders

such as hypertension and ulcers. This model has also been applied to

bipolar disorder. In a diathesis-stress model, there is a susceptibility (the

diathesis) for the disorder. An individual who has a diathesis is at risk for the

disorder but may not show signs of the disorder unless there is sufficient

stress. In this model, a genetic or biochemical predisposition toward the disorder

(the bipolar diathesis) may lie dormant until stress triggers the emergence

of the illness. The stress may be psychosocial, biological, neurochemical,

or a combination of these factors.

A diathesis-stress model can also account for some of the recurrent episodes

of mania in bipolar disorder. Investigators suggest that positive life

events, such as the birth of a baby or a job promotion, as well as negative life

events, such as divorce or the loss of a job, may trigger the onset of episodes

in individuals with bipolar disorder. Stressful life events and the social

rhythm disruptions that they cause can have adverse effects on a person’s

circadian rhythms. Circadian rhythms are normal biologic rhythms that

govern such functions as sleeping and waking, body temperature, and oxygen

consumption. Circadian rhythms affect hormonal levels and have significant

effects on both emotional and physical well-being. For those reasons,

many clinicians encourage individuals with bipolar disorder to work

toward maintaining consistency in their social rhythms.

More recently, investigators have compared the course of bipolar disorder

to kindling, a process in which epileptic seizures increase the likelihood

of further seizures. According to the kindling hypothesis, triggered mood

episodes may leave the individual’s brain in a sustained sensitized state that

makes the person more vulnerable to further episodes. After a while, external

factors are less necessary for a mood episode to be triggered. Episode

sensitization may also account for rapid-cycling states, in which the individual

shifts from depression to mania over the course of a few hours or days.

generations are affected by bipolar disorder. Serotonin, norepinephrine,

and dopamine, brain chemicals known as neurotransmitters that regulate

mood, arousal, and energy, respectively, may be altered in bipolar disorder.

A diathesis-stress model has been proposed for some psychosomatic disorders

such as hypertension and ulcers. This model has also been applied to

bipolar disorder. In a diathesis-stress model, there is a susceptibility (the

diathesis) for the disorder. An individual who has a diathesis is at risk for the

disorder but may not show signs of the disorder unless there is sufficient

stress. In this model, a genetic or biochemical predisposition toward the disorder

(the bipolar diathesis) may lie dormant until stress triggers the emergence

of the illness. The stress may be psychosocial, biological, neurochemical,

or a combination of these factors.

A diathesis-stress model can also account for some of the recurrent episodes

of mania in bipolar disorder. Investigators suggest that positive life

events, such as the birth of a baby or a job promotion, as well as negative life

events, such as divorce or the loss of a job, may trigger the onset of episodes

in individuals with bipolar disorder. Stressful life events and the social

rhythm disruptions that they cause can have adverse effects on a person’s

circadian rhythms. Circadian rhythms are normal biologic rhythms that

govern such functions as sleeping and waking, body temperature, and oxygen

consumption. Circadian rhythms affect hormonal levels and have significant

effects on both emotional and physical well-being. For those reasons,

many clinicians encourage individuals with bipolar disorder to work

toward maintaining consistency in their social rhythms.

More recently, investigators have compared the course of bipolar disorder

to kindling, a process in which epileptic seizures increase the likelihood

of further seizures. According to the kindling hypothesis, triggered mood

episodes may leave the individual’s brain in a sustained sensitized state that

makes the person more vulnerable to further episodes. After a while, external

factors are less necessary for a mood episode to be triggered. Episode

sensitization may also account for rapid-cycling states, in which the individual

shifts from depression to mania over the course of a few hours or days.