Cyclothymia, or cyclothymic disorder, is a mood disorder characterized by the co-occurrence of hypomanic and depressive symptoms over a period of at least two years, or one year in children and young adults. Symptoms must not meet the diagnostic criteria for manic/depressive episodes.^[1] Cyclothymia is considered a mild form of bipolar II disorder.^[2] There is evidence that cyclothymia may be the most common form of bipolar disorder.^[3]

• In 1882, cyclothymia was characterized by recurring mood cycles. This was accomplished by Karl Ludwig Kahlbaum.
  • Cyclothymia contains episodes, both of which occur in a milder form than in bipolar disorder:
    • Melancholic episodes
    • Manic episodes

• In 1980, cyclothymia was included to the DSM.^[3]

• Cyclothymia has been conceptualized in a variety of ways:^[4]
  • As a subtype of bipolar disorder
  • As a temperament
  • As a personality trait
  • As a personality disorder

• The two defining features of the disorder, according to DSM-5, are:
  • The presence of depressive episodes
  • The presence of hypomania

• Cyclothymia is classified by the DSM-V as a mild form of bipolar II disorder.^[2][5]
• There is disagreement among experts in the field of psychiatry as to whether this is an appropriate definition, or whether cyclothymia is actually better understood as a general instability of mood.^[6]
• Cyclothymia has been conceptualized to include other characteristics such as:^[7]
  • Mood reactivity
  • Impulsivity
  • Anxiety

• Conditions that are commonly comorbid with cyclothymia include:^[8]
  • ADHD
  • Anxiety disorders

• Cyclothymia must be differentiated from other disorders that present with similar symptomatology, including:^[2][5]
  • Major depression
    • Patients with cyclothymia can be distinguished from patients with major depression based on an earlier age of onset, a higher likelihood of having a family history of bipolar disorder, and a higher incidence of sleep disturbances.^[9][10]
  • Bipolar disorder
    • Cyclothymia can be distinguished from bipolar disorder by the relatively minimized intensity of the mood-altering episodes patients experience and a younger age of onset.^[5][10]

• The prevalence of cyclothymic disorder is 400-1,000 per 100,000 (0.4%-1%) of the overall population.^[3][11][5]
• There is evidence that suggests cyclothymia may be the most common form of bipolar disorder.
• The estimated lifetime prevalence rate was found to be between 5%-8%, whereas other studies suggest a much lower rate ranging from 0.4%-2.5%.^[6]

• Cyclothymia is most common in young adults.^[5]

• Men and women are equally likely to be affected by cyclothymia, though women may be more likely to seek treatment.^[2][11]

• No racial predilection of cyclothymia has been observed.

• Risk factors for the development of cyclothymia include:^[2][5][12]
  • Being an adolescent
  • Childhood abuse
  • Having a mentally ill parent
  • Having problems at school
  • Genetic predisposition

• The cause of cyclothymic disorder is unknown.
• Genetics may play a role, as indicated by a range of twin studies involving dizygotic (fraternal) and monozygotic (identical) twins.
• There is a high likelihood that a patient with cyclothymia will have a family history of mood disorders.^[2]

• Cyclothymia usually manifests early in a patient’s life.^[2]
• Possible complications include a progression to bipolar disorder, though this occurs in less than half of cyclothymic patients.^[2]
  • Early intervention may allow patients to circumvent some of the complications associated with bipolar disorder.^[8]
• Cyclothymia may remain a chronic condition or disappear over the course of a patient’s life.^[2]

DSM-V Diagnostic Criteria for Cyclothymic Disorder^[5]

• Symptoms of cyclothymia include:^[2]
  • Periods of both mania (extreme mood elevation and energy) and depression (low mood and energy level) for at least two years, or one in children and young adults
  • Mood swings that are not as severe as those observed in bipolar disorder
  • Continuity of manic/depressive episodes (i.e., no more than 2 consecutive months without symptoms)

• A diagnosis of cyclothymia is made based on a patient’s mood history.^[2]

• One prominent barrier to a diagnosis is a lack of consensus among clinicians about the precise distinction between syndromal and subsyndromal depression and mania.^[11]

• Although no laboratory findings are diagnostic of cyclothymia, a healthcare provider may wish to order blood tests and/or urine tests in order to rule out other possible causes of mood swings.^[2]

• No imaging findings are diagnostic of cyclothymia, though limited evidence suggests that cyclothymia may be associated with activity in the left lingual gyrus.^[13]

The treatment of cyclothymia may involve medications.^[2]

• Medication
  • Medication may involve:^[2]
    • Mood-stabilizing drugs
    • Antidepressants
  • Commonly prescribed mood-stabilizers are:
    • Lithium
    • Anti-epileptic drugs
  • Clinical evidence also supports the use of such antipsychotic drugs as quetiapine.^[11]
  • Talk therapy is another source of treatment for cyclothymia.
    • Support groups may be helpful for patients suffering from cyclothymia.^[2][11]