The occurrence of bipolar manic depression, according to the American Psychiatric Association, is estimated to be in the 1.2% to 1.6% range with some experts contending it to be even higher in the 3% range. It is a chronic recurring illness that must be managed through out the lives of those who suffer from it. Unfortunately bipolar disorder goes undetected in many people who may suffer its effects before being diagnosed and treated.

There are 4 biological risk factors that may increase an individual’s chance of suffering from this devastating disease. They are as follows:

1. Genetic Factors - There is an abundance of evidence that supports the view that bipolar disorders have a strong genetic component. The rate

of bipolar disorder, for example, in relatives of people with bipolar disorders can be as much as 50 to 10 times higher than the rates found in the general population.

A National Institute of Mental Health study found that 25% of the relatives of people with bipolar manic depression had a bipolar or major depressive disorder. Studies of twins have shown a genetic marker for both bipolar depression and depressive disorders but the risk of illness is much higher for people who have the marker for bipolar disorder. Identical twins, who have the genetic marker, are more likely to both have bipolar disorder at about 78% to 80% while fraternal twins are only at 14% to 19% risk.

Unfortunately the

reason why this disease can be passed through family members is not fully understood. Recently researchers have identified two genes (G72 and G30) located on the long arm of chromosome 13 that are associated with bipolar disorder as well as schizophrenia.

2. Neurobiological Factors - Since the 1960s the neurotransmitters norepinephrine, dopamine, and serotonin have been the subject of many studies as factors in mania and depression. During a manic episode people who have bipolar manic depression have been shown to have plasma levels of norepinephrine and epinephrine that are much higher then when they are having a depressed or normal mood. The degree of dysphoria, anger, and anxiety corresponds to norepinephrine levels in people who are experiencing a manic

episode. Mood disorders are most likely a result of complex interactions among various chemicals, including neurotransmitters and hormones.

3. Neuroendocrine Factors - The hypothalamic-pituitary-thyroid-adrenal axis has been closely scrutinized in people with mood disorders. Hypothyroidism is known to be associated with depressed moods, and hypothyroidism is seen in some people who are experiencing rapid cycling bipolar disorder. There are some studies that suggest that thyroid hormone administration may help mood disorders in some people with bipolar disorder.

4. Neuroanatomical Factors - The brain pathways implicated in the pathophysiology of bipolar disorder are in the subregions of the prefrontal cortex and the medial temporal lobe. Dysregulation in the neurocircuits surrounding these areas have been viewed with the aid of magnetic resonance

imaging (MRI) and positron emission tomography (PET scan).

There are many factors that increase the risk for bipolar manic depression but from the biological perspective these are the four that medical and mental science believe are of major concern.

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