Bipolar II Disorder is a serious and chronic psychiatric illness characterized by sharp mood fluctuations, in which depressive episodes and hypomanic periods alternate. The fundamental difference from Bipolar I Disorder is the absence of fully developed manic episodes. This distinction directly affects diagnostic and treatment processes. The disorder may lead to impairments in functioning, decreased quality of life and increased risk of suicide. It usually begins during adolescence or early adulthood and follows a lifelong fluctuating course.

Clinically, Bipolar II Disorder is defined by the presence of one or more major depressive episodes and at least one hypomanic episode. While depressive episodes are severe, hypomania often goes unnoticed or is perceived positively due to increased productivity, which delays treatment-seeking. This complicates the recognition and management of the disorder.

DSM-5 Diagnostic Criteria for Bipolar II Disorder

According to DSM-5, the diagnosis of Bipolar II Disorder requires the following criteria:

• At least one hypomanic episode (lasting at least four days, with clearly increased energy, activity and irritable mood),
• At least one major depressive episode (lasting at least two weeks, with depressed mood, loss of interest, changes in appetite and sleep, decreased energy, feelings of worthlessness, suicidal thoughts),
• No history of a manic episode,
• Symptoms must cause significant impairment in social, occupational or personal functioning,
• Symptoms must not be attributable to a medical condition or substance use.

Hypomania is a period in which the individual experiences abnormally increased energy, expansive or irritable mood, but not severe enough to require hospitalization or present with psychotic features. For this reason, diagnosis is usually made retrospectively through patient history rather than clinical observation.

What Are the Symptoms of Bipolar II Disorder?

The symptoms of Bipolar II Disorder are examined in two main phases: depressive and hypomanic.

Major depressive episodes are the periods that most disrupt overall quality of life. Common symptoms include persistent sadness, feelings of emptiness, lack of energy, difficulty concentrating, sleep disturbances, appetite changes, feelings of worthlessness or guilt and suicidal ideation. These symptoms significantly impair functioning.

During hypomanic periods, the individual may appear unusually energetic, talkative, confident and creative. At the same time, irritability, distractibility, racing thoughts, decreased need for sleep and risky behaviors (such as overspending, reckless driving, increased sexual activity) may occur. However, these symptoms are not severe enough to completely impair daily functioning.

What Are the Causes (Etiology) of Bipolar II Disorder?

Bipolar II Disorder has a multifactorial etiology. Genetic, neurobiological, environmental and psychosocial factors all contribute to the development of the illness.

Genetic predisposition is the most prominent risk factor. The risk is approximately 8–10 times higher in first-degree relatives of individuals with bipolar disorder. Twin studies report a concordance rate of about 40% in monozygotic twins. Neurobiologically, dysregulations in monoamine neurotransmitters (particularly dopamine, serotonin and norepinephrine) contribute to mood regulation disturbances. Functional and structural changes in the limbic system have been identified in neuroimaging studies.

In addition, dysregulations in the hypothalamic-pituitary-adrenal (HPA) axis alter stress responses and create vulnerability to mood disorders. Childhood trauma, emotional neglect, family conflict and early life stressors also play a role in the onset of the disorder.

Risk Factors in Bipolar II Disorder

The main known risk factors for Bipolar II Disorder include:

• Family history of bipolar disorder
• Early-onset depressive episodes
• Frequent recurrent mood episodes
• Traumatic life events (particularly in early childhood)
• Mood changes associated with substances (alcohol, stimulants)
• Female gender (Bipolar II Disorder has been reported more frequently in women)

Some studies suggest that depressive episodes are more prominent in women, whereas hypomanic periods tend to be more pronounced in men.

How Is It Diagnosed?

The diagnosis of Bipolar II Disorder requires a detailed psychiatric evaluation. The greatest challenge in diagnosis is that hypomanic periods are often overlooked, as they are usually perceived positively and not seen as problematic by the individual.

During the diagnostic process, the individual’s history is carefully evaluated according to DSM-5 criteria. Differential diagnosis should include major depression, Bipolar I Disorder, borderline personality disorder, attention deficit hyperactivity disorder (ADHD) and substance-induced mood disorders. Suicide risk must always be assessed. Neuroimaging and biochemical tests may be employed when necessary.

How Is Bipolar II Disorder Treated?

Treatment of Bipolar II Disorder requires a long-term and holistic approach focusing on mood stabilization. It involves both pharmacotherapy and psychosocial interventions.

1. Pharmacological Treatment

Mood stabilizers form the cornerstone of treatment. The most commonly used agents include:

• Lithium: Effective in preventing both hypomanic and depressive episodes. It also reduces suicide risk.
• Lamotrigine: Effective in controlling depressive episodes, but has limited effect on hypomania.
• Valproate and carbamazepine: Preferred especially in mixed episodes or rapid cycling disorders.

Antidepressants should not be used alone; they must be combined with a mood stabilizer. Otherwise, the risk of switching into hypomania or rapid cycling increases. Atypical antipsychotics (such as quetiapine, lurasidone) may also be used in some cases.

2. Psychotherapy

In addition to pharmacological treatment, psychotherapeutic interventions positively influence long-term prognosis:

• Cognitive Behavioral Therapy (CBT): Aims at identifying and restructuring depressive thought patterns.
• Family-Focused Therapy: Educates the family about the illness and strengthens emotional support mechanisms.
• Interpersonal and Social Rhythm Therapy: Targets regulation of sleep, eating and activity routines.

3. Psychoeducation and Monitoring

Psychoeducation programs aimed at increasing patient awareness of the illness support treatment adherence and help prevent relapses. Regular psychiatric follow-up allows early detection of potential episodes.

Impact on Daily Life

Bipolar II Disorder significantly disrupts academic, occupational and social functioning, particularly during depressive episodes. Depression may lead to job loss, social isolation and neglect of self-care. Hypomanic periods, on the other hand, may cause risky behaviors and impulsive decisions that negatively affect the individual’s life.

Suicide risk is markedly high, especially during depressive phases. Research indicates that lifetime suicide attempt rates in individuals with bipolar disorder range between 30–40%. The disorder is also associated with comorbid anxiety disorders, substance use disorders and eating disorders.

Therefore, treatment of Bipolar II Disorder should not rely solely on medication; it must also include social support, psychoeducation, lifestyle adjustments and therapeutic interventions. Recognition of the illness by the individual, awareness of triggers and being in a supportive environment play a critical role in maintaining long-term well-being.