Health Conditions

What causes it?

The causes of bipolar disorder are not fully known.

Genes:

• Results from studies looking at twins and children that were adopted are consistent with the theory that bipolar disorder has a genetic component. For instance, those persons with a 1st degree relative (e.g. a parent or sibling) with bipolar disorder have a 15 to 35% greater risk of developing bipolar disorder.

Biochemical:

• There are also theories that biological factors, particularly changing levels of neurotransmitters are possible causes of bipolar disorder. One such theory is the monoamine theory which states that depressive episodes are caused by deficiencies in norepinephrine, serotonin, and dopamine. In addition, the theory states that manic episodes are caused by increasing levels of norepinephrine and dopamine. Two other neurotransmitters that may also play a part in bipolar disorder are GABA and glutamate.

• There can also be problems with regulation of hormones, which may induce episodes of bipolar disorder. For instance, individuals with an overactive thyroid gland may be more prone to manic episodes, while those with an underperforming thyroid gland may be more susceptible to depressive episodes.

Environmental:

• Another possible cause of bipolar disorder is the kindling phenomenon. Kindling occurs when a psychosocial stressor precedes the 1st episode of bipolar disorder. A psychosocial stressor could be as varied as working in a stressful workplace or driving in a heavy traffic jam. Future episodes occur spontaneously due to an increased sensitivity in the central nervous system, CNS, caused by the initial stressor.

• Substance abuse and sleep deprivation can also bring about manic episodes.