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Neurochemical Factors in Bipolar Disorder. Bipolar disorder is primarily a biological disorder that occurs in a specific area of the brain and is due to the dysfunction of certain neurotransmitters, or chemical messengers, in the brain.nvironmental Factors in Bipolar Disorder. 1  A life event may trigger a mood episode in a person with a genetic disposition for bipolar disorder. 2  Even without clear genetic factors, altered health habits, alcohol or drug abuse, or hormonal problems can trigger an episode.
The wide range of potential causes has lead to the development of numerous depression treatments. Biological Cause of Major Depressive Disorder. A change in brain activity is almost always associated with major depressive disorder. There is decreased activity in the left frontal lobe during depression and a rise in activity following stabilization of mood. These discrepancies between over-active and under-active regions of the brain are at the biological cause of major depressive disorder. Neurotransmitters Could Cause Depression The release and reuptake of neurotransmitters (serotonin, norepinephrine, and dopamine) in the brain is linked to a personâs mood.