Bipolar I Disorder | What Defines the Extreme Mood Shifts?

A manic episode is the defining feature of Bipolar I Disorder. It is not simply a feeling of happiness or high energy; it is a distinct period of abnormally and persistently elevated, expansive, or irritable mood and abnormally and persistently increased goal-directed activity or energy, lasting at least one week and present most of the day, nearly every day. During this period, three or more of the following symptoms are significant: inflated self-esteem or grandiosity, decreased need for sleep (e.g., feels rested after only three hours), more talkative than usual or pressure to keep talking, flight of ideas or subjective experience that thoughts are racing, distractibility, an increase in goal-directed activity (either socially, at work or school, or sexually), or psychomotor agitation. The episode is severe enough to cause marked impairment in social or occupational functioning or to necessitate hospitalization to prevent harm to self or others, or there are psychotic features. From a neurobiological perspective, this state is associated with significant alterations in brain activity, particularly in regions responsible for emotional regulation and executive function, such as the prefrontal cortex. There is often a surge in neurotransmitters like dopamine, which contributes to the heightened energy, reward-seeking behavior, and sometimes psychosis experienced during mania.

While not required for the diagnosis of Bipolar I Disorder (the presence of one manic episode is sufficient), major depressive episodes are a common component of the illness. A major depressive episode involves a period of at least two weeks during which there is either a depressed mood or the loss of interest or pleasure in nearly all activities, known as anhedonia. Additional symptoms include significant weight loss or gain, insomnia or hypersomnia, psychomotor agitation or retardation, fatigue or loss of energy, feelings of worthlessness or excessive guilt, diminished ability to think or concentrate, and recurrent thoughts of death or suicide. These symptoms cause clinically significant distress or impairment. Brain imaging studies during these episodes often show decreased activity in the prefrontal cortex and altered function in limbic structures like the amygdala and hippocampus, which are central to processing emotions and memory. The balance of neurotransmitters such as serotonin, norepinephrine, and dopamine is also disrupted, contributing to the profound low mood and lack of motivation.

Bipolar I Disorder is understood to be a multifactorial condition with no single cause. There is a strong genetic component, as the disorder frequently runs in families. Specific genes have been identified that may increase susceptibility, many of which are involved in neurotransmitter regulation and neuronal signaling. Neurobiologically, imbalances in key neurotransmitters—including dopamine, serotonin, and norepinephrine—are considered central to the mood episodes. Furthermore, structural and functional differences in the brain are observed in individuals with the disorder. Areas involved in emotional processing and executive control, such as the prefrontal cortex, amygdala, and hippocampus, often show altered volume and connectivity. Environmental factors, such as significant life stress, trauma, or substance use, can act as triggers for the onset of mood episodes in genetically predisposed individuals.

The diagnosis of Bipolar I Disorder is made through a comprehensive clinical evaluation by a qualified mental health professional, such as a psychiatrist. There is no single blood test or brain scan that can definitively diagnose the condition. The diagnosis relies on criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The core requirement is the documented presence of at least one manic episode. The clinician will conduct a detailed interview to gather information about the individual's symptoms, personal history, and family history. It is also crucial to rule out other medical or psychiatric conditions that can mimic mania, such as thyroid disorders, substance use disorders, or schizophrenia. The presence, history, and severity of depressive or hypomanic episodes are also assessed to form a complete clinical picture.

The primary distinction between Bipolar I and Bipolar II Disorder lies in the severity of the elevated mood episodes. Bipolar I Disorder is defined by the occurrence of at least one full-blown manic episode. These manic episodes are severe and cause significant impairment in functioning, may involve psychosis (delusions or hallucinations), and often require hospitalization. In contrast, Bipolar II Disorder is characterized by at least one hypomanic episode and at least one major depressive episode. A hypomanic episode is a less severe form of mania. While it involves a clear change in mood and functioning that is observable to others, it is not severe enough to cause major impairment in social or occupational life or to necessitate hospitalization. Therefore, the critical difference is mania (in Bipolar I) versus hypomania (in Bipolar II).