Schizophrenia is a serious mental illness characterized by incoherent or illogical thoughts, bizarre behavior and speech, and delusions or hallucinations, such as hearing voices. The age of onset is typically between the late teens and mid-30s.

A middle-aged man walks the streets of New York City with aluminum foil on the inside of his hat so Martians can’t read his mind. A
young woman sits in her college classroom and hears the voice of God telling her she is a vile and disgusting person. You try to strike up a conversation with the supermarket bagger, but he stares at you vacantly and will say only one or two words in a flat, toneless voice. Each of these people may have schizophrenia.

Schizophrenia is a complex syndrome that inevitably has a devastating effect on the lives of the person affected and on family members. This disorder can disrupt a person’s perception, thought, speech, and movement: almost every aspect of daily functioning.

Toward the end of the 19th century, the German psychiatrist Emil Kraepelin (1899) built on the writings of Haslam, Pinel, and Morel (among others) to give us what stands today as the most enduring description and categorization of schizophrenia.

Two of Kraepelin’s accomplishments are especially important. First, he combined several symptoms of insanity viewed as reflecting separate and distinct disorders.: Catatonia (alternating immobility and excited agitation), hebephrenia (silly and immature emotionality). Paranoia (delusions of grandeur or persecution). Kraepelin thought these symptoms shared similar underlying features and included them under the Latin term dementia praecox.


Identifying Symptoms for Schizophrenia.

Schizophrenia is a number of behaviors or symptoms that aren’t necessarily shared by all people who are given this diagnosis. Kraepelin described the situation when he outlined his view of dementia praecox in the late 1800s:

“The complexity of the conditions which we observe in the domain of dementia praecox is very great. So that their inner connection is at first recognizable only by their occurring one after the other in the course of the same disease. In any case certain fundamental disturbances, even though they cannot for the most part be regarded as characteristic. Yet return frequently in the same form, but in the most diverse combinations.

This mix of symptoms was also highlighted by Bleuler in the title of his 1911 book, Dementia Praecox or the Group of Schizophrenias, which emphasizes the complexity of the disorder.

The term psychotic behavior has been used to characterize many unusual behaviors. Although in its strictest sense it usually involves delusions (irrational beliefs) and/or hallucinations (sensory experiences in the absence of external events). Schizophrenia is one of the disorders that involve psychotic behavior. Schizophrenia can affect all the functions we rely on each day.

1. Positive Symptoms.

Positive symptoms of schizophrenia, which are the more obvious signs of psychosis. These include the disturbing experiences of delusions and hallucinations. Between 50% and 70% of people with schizophrenia experience hallucinations, delusions, or both.

1. Delusions.

A belief seen by most members of a society as a misrepresentation of reality referred as a disorder of thought content, or a delusion. Because of its importance in schizophrenia, delusion also referred as “the basic characteristic of madness”. If, for example, you believe that squirrels are aliens sent to Earth on a reconnaissance mission, you would be considered delusional.

2. Hallucinations.

Have you ever thought you heard someone call your name, only to discover that no one was there? Did you ever think you saw something move by you, yet nothing did? We all have fleeting moments when we think we see or hear something that isn’t there. For many people with schizophrenia, however, these perceptions are real and occur regularly. The experience of sensory events without any input from the surrounding environment is a hallucination. The case of David illustrates the phenomena of hallucinations, as well as other disorders of thought that are common among people with schizophrenia.

2. Negative Symptoms.

The negative symptoms usually indicate the absence or insufficiency of normal behavior. They include apathy, poverty of (i.e., limited) thought or speech, and emotional and social withdrawal. And approximately 25% of people with schizophrenia display these symptoms.

1. Avolition.

Avolition is the inability to initiate and persist in activities. People with this symptom (also referred to as apathy) show little interest in performing even the most basic day-to-day functions, including those associated with personal hygiene.

2. Alogia.

Alogia refers to the relative absence of speech. It may experienced by some people with schizophrenia. Like some mood disorders, anhedonia signals an indifference to activities that people would consider pleasurable, including eating, social interactions, and sexual relations.

3. Affective Flattening.

Imagine that people wore masks at all times: You could communicate with them verbally, but you wouldn’t be able to see their emotional reactions. Approximately one-quarter of the people with schizophrenia exhibit what is flat affect. They may stare at you vacantly, speak in a flat and toneless manner, and seem unaffected by things going on around them. However, although they do not react openly to emotional situations, they may be responding on the inside.

Diagnostic Criteria for Schizophrenia.

A. Two (or more) of the following, each present for a significant portion of time during a 1-month period (or less if successfully treated). At least one of these must be (1), (2), or (3):
1. Delusions.
2. Hallucinations.
3. Disorganized speech (e.g., frequent derailment or incoherence).
4. Grossly disorganized or catatonic behavior.
5. Negative symptoms (i.e., diminished emotional expression)

B. For a significant portion of the time since the onset of the disturbance, level of functioning in one or more major areas. Such as work, interpersonal relations, or self-care, is markedly below the level achieved prior to the onset.

C. Continuous signs of the disturbance persist for at least 6 months. This 6-month period must include at least 1 month of symptoms (or less if successfully treated) that meet Criterion A (i.e., active-phase symptoms). They may include periods of prodromal or residual symptoms. During these prodromal or residual periods, the signs of the disturbance may be manifested by only negative symptoms. Or by two or more symptoms listed in Criterion A present in an attenuated form. (E.g., odd beliefs, unusual perceptual experiences).

D. Schizoaffective disorder and depressive or bipolar disorder with psychotic features have been ruled out because either

  1. No major depressive or manic episodes have occurred concurrently with the active-phase symptoms; or
  2. If mood episodes have occurred during active-phase symptoms, they have been present for a minority of the total duration of the active and residual periods of the illness.

E. The disturbance is not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication). Or another medical condition.

F. If there is a history of autistic spectrum disorder or a communication disorder of childhood onset. They made additional diagnosis of schizophrenia only if prominent delusions or hallucinations, in addition to the other required symptoms of schizophrenia that are also present for at least 1 month.
Specify if: With catatonia.


David H. Barlow, V. Mark Durand. Abnormal Psychology, An Integrative Approach. (7th ed).

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