Unipolar depression and bipolar depression are both categorized as mood disorders in the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5. Mood disorders are characterized by distorted fluctuations in emotion and mood that interfere with normal, daily functioning. An individual that possesses a mood disorder has difficulty regulating and staying in control of their emotions.
The Latin prefix “uni” means one, or single, while the Latin prefix “bi” means having two. True to their prefixes, unipolar depression is comprised of one type of depression, while bipolar depression is comprised of both depression and mania. Mania is a mental disorder that is exemplified by intervals of euphoria, exhilaration, illusion, and an overactive mental state. Symptoms of mania can include excessive happiness, elevated self-confidence, racing thoughts, impulsivity, restlessness, and aggressive behavior. Unipolar depression lacks mania and is comprised solely of depressive symptoms. Unipolar depression depicts that moods are centralized around one depressive pole, while bipolar depression vacillates between two poles, a depressive low and a manic high.
Bipolar disorder does not have a single cause and is thought to result from genetic factors, hormonal or chemical imbalances in the brain, and environmental factors, such as stressors or trauma. It is possible that one could possess a genetic predisposition for bipolar depression, which draws out the disorder when triggered by an environmental stressor. Similarly, the precise cause of unipolar depression is also unknown. It is believed that a mixture of genetic factors and stress impacts chemistry in the brain and hormonal balance, which then impacts mood stability.
Unipolar and bipolar depression share some similarities, as symptoms of unipolar depression match the depressive pole in Bipolar depression. Both types of depression are typified by tearfulness, feelings of helplessness, negativity, and disrupted eating and sleeping habits. Loss of interest in once pleasurable activities, irritability, low energy, lack of concentration at work or school, and low self-esteem are other shared characteristics. Both unipolar and bipolar depression vary in frequency and intensity and poses a potential threat for suicide.
Despite their similarities, unipolar and bipolar depression have contrasting symptoms and characteristics. For example, individuals with unipolar depression have disrupted sleeping patterns, poor appetite, and weight loss, while those with bipolar depression sleep excessively or not at all, have elevated appetite, and experience weight gain. Bipolar depression is often accompanied by a co-occurring anxiety disorder, with symptoms of anxiety being of greater magnitude than when present in unipolar depression alone. Bipolar depression has a higher suicide rate than unipolar depression, which is likely due to the multitude of symptoms that fluctuate with depression, including mania, anxiety, and psychosis.
Bipolar depression can be difficult to diagnose, as it may look like unipolar depression when an individual is in a depressive state. An individual can experience depressive symptoms for many years before experiencing a manic episode, making diagnosis more complex. Thus, obtaining a thorough family history is another helpful diagnostic tool.
Treatment guidelines differ greatly between the two diagnoses, which is why it is critical for one to have an accurate diagnosis. Treatment for bipolar depression seeks to reduce the frequency and severity of manic and depressive episodes. Bipolar depression is treated with a combination of psychotherapy and psychotropic medication. Bipolar depression is treated with mood stabilizers, such as lithium, an antimanic drug, or with antipsychotic drugs, or with a combination of both. This treatment protocol works to ameliorate depressive symptoms without causing a manic episode. If an individual with bipolar depression is prescribed antidepressant medication in the absence of a mood stabilizer, mood instability is quickened and a manic episode could be triggered. Unipolar depression is treated with antidepressants, psychotherapy, or a combination of both.
Unipolar depression and bipolar depression are inherently different in that unipolar depression lacks manic symptoms, thus representative of “uni”, or a single pole. In contrast, bipolar depression is comprised of both depressive and manic symptoms, representative of the Latin prefix, “bi”, or having two poles. Despite some similarities in origin and symptoms, they diverge in other symptoms and in treatment options.