It is difficult to pinpoint any conclusive factors that cause manic-depression, also known as bipolar disorder. This disorder is differentiated by varying periods of depression and mania. The severity of depression may range from mild to clinical depression. The clinical depression phases are defined as lasting for at least for two weeks time. During this phase, depressed people may suffer gloominess, sleeplessness, laziness, dietary disturbances, suicidal inclinations, and dejection.

Bipolar disorder does not denote a single type of depression. It encompasses various episodes consisting of depressive, manic, hypomanic, and mixed conditions. These phases of mood alternate and are interspersed with normal mood generally. But in some persons, mania and depression happen in rapid succession. It is called rapid cycling.

Depending upon the category and strength of the disorder, it has been sub-categorized as bipolar I, bipolar II and cyclothymia. In bipolar I type of disorder, people undergo one or more manic phases along with major depressive episode or even without it. Bipolar II disorder is associated with hypomanic episodes along with at least one major depressive episode. Cyclothymia is still difficult to define. It entails previous occurrence of hypomanic episodes with phases of depression which do not meet up with conditions of the major depressive episodes.

Common Causes of Manic Depression

Biological Causes:

Genetic factors: Bipolar disorder is believed to be hereditary. The generations carry the genetic information. A person with this hereditary propensity is prone to get bipolar disorder when there are triggers such as medicinal dependency and overuse, or undergoes trauma. Peoples of first generations are more likely to get disorder from their depressed parents than those people whose parents did not suffer any depression.

Research has been made on twins. In the case of identical twins, chances are very high for the second twin to get depressive disorder when the first twin suffers from it. Particularly in the case of bipolar depressive disorder, both the twins are equally prone to get this illness. In fraternal twins, the chances are appreciably low. There is clinching proof that manic depression is heritable and that significant risks are there to get the illness in subsequent generations.

Brain Messengers: Research shows that there is a connection between mood changes and neurotransmitters. Medications given to change concentrations of neurotransmitters have also helped in giving relief to people with mood disorders.

The three messengers of brain, namely serotonin, dopamine and norepinephrine, are the three neurotransmitters that will help control of our moods. It is assumed that inequalities in these bio-chemicals are the causative factors for mood disorders of manic depression. Research shows that the very nature of imbalance is the problem, which means a specific level of a particular neurotransmitter is not as important as to its relative quantity with regard to other neurotransmitters.

Cerebral Activity: Magnetic Resonance Imaging scans of the brain show considerable variations between the chemical activity of normal brain and a bipolar depressed brain. General chemical activity and blood supply to both sides of the brain appeared equal in normal people. But for people with manic depression, some parts of their brain are more active than other parts of their brain.

Effect of Hormones: Some chemical substances are found to be out of balance relative to others in people with bipolar disorder. Higher concentrations of cortisol, and thyroid chemicals are assumed to cause mood disorders.

Rhythm Disturbances : Our internal clock is attuned to sunlight. Accordingly, the clock shuts down our overall activity during nights and sleep is induced. These sleep and wake patterns are known as circadian rhythms. Now, interruptions to circadian rhythms have been attributed bipolar disorder. The biological clock that controls these sleep-wake rhythms becomes unusually erratic with bipolar disorder.

Stress Causes:

For all psychological, behavioral and situational factors, occurrences in life that cause stress are considered to be the main factor for progress of illness in bipolar disorder. These may include bereavement, loss of job, birth of a child, financial inadequacies, marital problems, social status, parental stress, occupational anxieties etc. Any activity that brings stress to a person is a causative factor for manic depression.

Once this disorder sets in a person, biological and psychological factors start playing a role and a cycle starts and the person becomes more depressed.