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Diagnostic Differences Between Bipolar Disorder and Schizophrenia

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Updated June 10, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Psychosis is a hallmark symptom of schizophrenia. People with bipolar I disorder can have psychotic symptoms - hallucinations and delusions - during mania and/or depression, and those with bipolar II during depression. So the two illnesses of bipolar and schizophrenia can share a set of serious symptoms, but when distinguishing between the two disorders, doctors look at the differences between symptoms, and also give different weight to some of the symptoms that are shared.

Note: This article looks at symptoms in adults only.

Most Important Symptoms of Schizophrenia

  1. For most of a month, a patient must have two of these symptoms:

    • Delusions

    • Hallucinations

    • Disorganized speech - derailment or incoherence (also known as word salad) where there is no connection between spoken words at all. (For example: Coffee abstract welcome tiptoes glue kitchen puppy.)

    And if only one of these is present, one of the following must also appear:

    The negative symptoms of schizophrenia include:

    Only one of these symptoms is required for diagnosis if the delusions are bizarre, or the hallucinations are characterized by keeping a running commentary—or are two voices conversing with each other.

  2. At the same time, there's a marked decrease in at least one important area of functioning, such as:

    • Work
    • School
    • Relations to others
    • Self-care such as cleanliness
In addition to the month of acute symptoms, the overall disturbance must have persisted for at least six months.

Most Important Symptoms of Bipolar Disorder

None of the symptoms of delusions, hallucinations, and disorganized speech and behavior have to be present in someone to be diagnosed with bipolar disorder, although they may be present. In fact, the only requirement for a diagnosis of bipolar I disorder is that the patient has had one manic episode; though depression is also common, it isn't required for a diagnosis. And for bipolar II, the requirements are almost as simple: no manic episodes, at least one hypomanic episode, and at least one major depressive episode.

Definitions and symptoms:

In bipolar disorder, another requirement is that the symptoms cause significant problems with occupational and/or social functioning. This is similar to #2 under schizophrenia, but the reasons for the impairment are, in general, profoundly different.

To summarize the differences between the diagnostic requirements for the two illnesses:

Diagnostic Differences Between Schizophrenia and Bipolar
Schizophrenia - Required SymptomsBipolar Disorder - Required Symptoms
1. Two or more of these symptoms:
  • Required: Hallucinations or delusions. May be required: disorganized speech, abnormal psychomotor behavior, negative symptoms
2. Significant decrease in the level of occupational, social and/or personal functioning.
Bipolar I: A single manic episode, which may or may not include psychosis.

Bipolar II: At least one hypomanic episode, and at least one major depression episode (which may or may not include psychosis).

Both: Clinically significant disruption with occupational and/or social functioning.

Schizophrenia - DurationBipolar Disorder - Duration
Overall, six months. During that time, the symptoms listed in #1 must be present most of the time for at least one month (can be less if early treatment succeeds in controlling them). Bipolar I: Manic episode lasting at least 1 week.

Bipolar II: Hypomanic episode lasting at least 4 days, and depressive episode lasting at least 2 weeks.

Illnesses Related to Schizophrenia

Additional Form of Bipolar Disorder
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