Differences Between Bipolar Disorder and Schizophrenia

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

Most Important Symptoms of Schizophrenia

These are the main symptoms of schizophrenia in adults:

 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."

If only one of these symptoms is present, one of the following must also appear:

  • Extreme and abnormal psychomotor behavior, which includes catatonia
  • Negative symptoms
  • Alogia—a reduction in the amount of speech or quality of speech
  • Flattened affect—having little or no emotion
  • Anhedonia—loss of pleasure
  • Avolition—severe lack of initiative

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

  • Work
  • School
  • Relations with 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 for 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.

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

Diagnostic Differences

Here's a summary of the differences between the diagnostic requirements for the two illnesses:

Diagnostic Differences Between Schizophrenia and Bipolar
SchizophreniaRequired SymptomsBipolar DisorderRequired Symptoms

1. Two or more of these symptoms:

  • Required: Hallucinations or delusions
  • May be required: Disorganized speech, abnormal psychomotor behavior, negative symptoms
2. A 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 depressive episode (which may or may not include psychosis)

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

 

SchizophreniaDurationBipolar DisorderDuration
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.

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