There exists a mental malady manifesting two extremes of behavior: high, euphoric mood called mania, versus low, sad mood called depression.  This condition has been termed bipolar disorder, or "bipolar affective disorder," since the disease turns on the mood or affect of an individual.  It is also known as manic depression. 

Manic behavior may contain inappropriately elevated mood, absence of need for sleep, megalomania (psychosis--delusions of grandeur, wealth, or power), flight of ideas (racing thoughts),  logorrhea (talkativeness), irritability, hypersexuality, and other signs.  A lesser form without psychotic features called hypomania is less destructive to the target person, family, and friends.

Depression manifests as anhedonia (loss of interest in sex, hobbies, personal care), anxiety, insomnia, hypersomnia (excessive sleep), restlessness, feelings and delusions of guilt, delusions of worthlessness, hopelessness, lack of energy, poor concentration, poor personal hygiene, memory issues, chronic complaints, death thoughts ("I want to die."), suicidal thoughts, plans for suicide, suicide attempts, and suicide.

A person ill with bipolar affective disorder may cycle from mania to depression and back repeatedly only a few times in their life, or cycle several times a day or week (rapid cycling).  Two-thirds of those with the disorder initially have periods of lucidity between mood fluctuations, whereas 1/3 are continuously symptomatic.  Some remain stuck in depression for months or years, only to become manic when exposed to an antidepressant or ginko biloba.  Rapid cycling predominates as the disease advances.

The classic form of bipolar affective disorder, depression  cycling with mania, is  called Type I.  Type II is associated with drug abuse (especially alcohol); personality disorders, i.e. obsessive compulsive personality; post-traumatic stress disorder, and/or anxiety.¹  A  mild form of Type II is called cyclothymia, with mood swings between hypomania and dysthymia (a milder but longer lasting form of depression).

Studies indicate that concordance for bipolar affective disorder is greatest in identical twins: if  one identical twin develops the disorder, there is a 60 to 80% chance the other matched twin will develop it, much higher than rates seen for fraternal twins.  Since identical twins share the same genetic makeup, a shared gene responsible for the phenotype might exist.  However, the single gene hypothesis has given way to a belief that several genes may be involved in the biosynthesis of this disease, with the Human Genome Project at the forefront of this research.^2,3 

Additionally,  many studies suggest environmental factors play a role in the etiology of manic depression,  including an increased frequency of childhood sexual and physical abuse recorded in the histories of men and women suffering from the  disorder. Men develop  mania at an earlier age, while women predominate in adult years with depression.  Mood symptoms associated with the reproductive cycle have been observed in Type I females.⁴  MRI, PET, and fMRI scanning show differences between the bipolar and nonbipolar brain.⁵

Manic depression can start in childhood, teen years, or young adulthood.  Proper, attentive evaluation and treatment of people with this complex of symptoms is mandatory.   Without treatment the course of the disorder may lead to disruption of family, social circles, loss of employment or suicide.  Medication includes mood stabilizers, such as lithium (responsible for a dramatic reduction in the rate of suicide), depakote (anticonvulsant), lamotrigine (anticonvulsant), or atypical antipsychotics (quetiapine) or any of a number of other effective prescription medications available clinically. 

Cognitive Behavioral Therapy and other psychosocial treatments are helpful.  Occasionally inpatient treatment is necessary to protect the bipolar individual from self-harm or harming others, under the care and guidance of a psychosocial health care team.  With proper treatment, a patient with bipolar affective disorder has an excellent chance of returning fully functional to family, friends, workplace, and society.