The root causes of BD disorder are multifactorial, with genetics being the strongest. Identical twins have a 50% correlation. However, genetic predisposition does not guarantee the onset of the disorder.
The age of onset of bipolar disorder varies. For both BP I and BP II, the age range is from childhood to about 50 years, with a mean age of about 21 years. Individuals are between 15 and 19 years old when bipolar disorder emerges. The second most frequent age range of onset is 20–24 years. At least half of all cases start before age 25. Bipolar disorder impacts various demographics, including genders, races, and socioeconomic groups.
The lifelong prevalence of bipolar disorder in the United States ranges from 1% to 1.6%. WHO determined the aggregate global lifetime prevalence for bipolar I disorder: 0.6%.
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Impact of Genetics on Bipolar Disorder
Bipolar disorder tends to run in families. Children with a parent or sibling who has bipolar disorder are four to six times more likely to develop the illness in comparison with the general population.
The current research indicates that the genetic component of bipolar appears to be complex, with multiple genes being involved. Those studies suggest complex gene interaction and genetic heterogeneity, with different genes being implicated in the onset of bipolar disorder in different families.
Scientists have shown that some people have a genetic predisposition to develop bipolar disorder. However, not everyone with an inherited vulnerability develops the illness.
The genetic predisposition can be compared to someone walking on ice; in some cases, the ice may be thin but won’t break if the person moves smoothly. On the other hand, people without genetic predisposition but with triggering physical illnesses and/or stressful life events can develop bipolar disorder.
Genetics are not the only risk factor for bipolar disorder. Studies of identical twins have indicated that the twin of a patient with bipolar illness does not always develop the disorder; only 50% of the twins will develop the illness.
Bipolar Disorder in Twin studies
Scientists know the role of genetic factors. Twin, family, and adoption studies all show that bipolar disorder has a genetic component. In fact, first-degree relatives of a person with bipolar disorder are approximately seven times more likely to develop this disorder than the rest of the population.
Influence of Environmental Factors on Bipolar Disorder
The external factors can set off the onset of bipolar disorder. Psychiatrists call these factors triggers. Triggers can set off new episodes of mania or depression or make existing symptoms worse. Such triggering factors as stressful life events, sleep deprivation, and substance abuse can set off the onset of bipolar disorder in someone with a genetic vulnerability. These events tend to involve drastic or sudden life changes, exposing an individual to a high level of emotional tension. Psychiatrists also say that the events could be seasonal changes, sleep deprivation, use of drugs, getting married or losing a partner or loved one, losing a job, etc.
Race-related differences in incidence: no racial predilection exists.
Psychological Factors in Bipolar Disorder
Psychodynamic factors also play an important role in bipolar disorder. The psychoanalytical observations suggest that the mania serves as a defense against the feelings of depression. Melanie Klein was one of the major proponents of this formulation. Other psychodynamic-based studies found that bipolar patients had personality disturbances and a higher level of neuroticism.
Physical Illnesses and their Impact on Bipolar Disorder
Some organic diseases, for example, hyperthyroidism, illnesses of the central nervous system, and intoxication, can lead to similar symptoms as bipolar disorder. The diagnosis of bipolar disorder includes a profound anamnesis, physical examination, a battery of tests, and EEG, as well as a brain scan to exclude an organic cause.
Substance Abuse and Bipolar Disorder
Another risk factor for bipolar disorder is the abuse of alcohol or drugs. Studies show that about 50% of people with bipolar disorder have a substance abuse or alcohol problem. Also, people suffering from bipolar disorder tend to use alcohol or drugs, especially during depressive periods, in an attempt to enhance their mood. Conversely, manic episodes’ recklessness leads to substance misuse.
