How are bipolar disorders distinguished from depression?

The core distinction between bipolar disorders and major depressive disorder is the presence of manic or hypomanic episodes. The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders identifies manic symptoms as a distinct period of abnormally elevated, expansive, or irritable mood accompanied by increased energy or activity, decreased need for sleep, pressured speech, grandiosity, and risky behavior. Hypomania shares similar features but is shorter or less severe and does not cause frank psychosis or the major functional decline that characterizes a full manic episode.

Diagnostic criteria and clinical features
Bipolar I disorder requires at least one manic episode, while bipolar II disorder requires at least one hypomanic episode and at least one major depressive episode, according to the American Psychiatric Association. Major depressive disorder is diagnosed when a person experiences one or more major depressive episodes without any history of manic or hypomanic episodes. Because depressive episodes are common to both conditions, accurate diagnosis depends on careful assessment of past periods of elevated mood, energy, or behavior that patients or families may not recognize as clinically important. Kay Redfield Jamison, Johns Hopkins University School of Medicine, has written extensively about the challenges of recognizing hypomania and the clinical importance of distinguishing bipolar depression from unipolar depression in order to select appropriate long-term treatment.

Causes, risks, and consequences
Research summarized by the National Institute of Mental Health indicates that bipolar disorders arise from a combination of genetic vulnerability, neurobiological differences, and environmental triggers such as stress or substance use. Family studies and molecular genetics point to stronger heritability in bipolar disorder compared with most forms of unipolar depression, but no single cause explains every case. Neuroimaging and neurochemical research suggest alterations in mood regulation circuits and neurotransmitter systems across both bipolar disorder and major depression.

Clinically, the distinction matters because consequences and treatment differ. Bipolar disorders carry an elevated risk of mood instability, recurrence, and suicidal behavior; functional impairment may alternate between depressive lows and risky behavior during mania. Antidepressant monotherapy can induce mania or rapid cycling in some people with bipolar disorder, which is why treatment guidelines from the American Psychiatric Association recommend mood stabilizers or certain antipsychotics as foundational therapies, often combined with psychotherapy.

Cultural, environmental, and territorial nuances
Cultural factors shape how mood states are described, whether hypomanic behavior is perceived as creativity or pathology, and when help is sought. The World Health Organization highlights that depression is a leading cause of disability worldwide and that access to diagnosis and long-term mood-stabilizing treatments varies dramatically between high-income and low-income regions. In many settings, limited availability of lithium and specialized psychiatric care leads to underdiagnosis or misdiagnosis, with distinct implications for outcomes and public health planning.

Clear differentiation between bipolar disorders and depression therefore depends on thorough clinical history, awareness of hypomanic symptoms, and attention to genetic and environmental context. Accurate diagnosis guides safer, more effective treatment choices and reduces the risk of preventable harms.