6.1 Diagnosis of Schizophrenia

As the biological criteria for most of the psychiatric disorders are not available, the diagnosis of schizophrenia is primarily based on the clinical phenomenology (1). However, the clinical symptoms overlaps schizophrenia with other psychosis has been a challenge for a rigorous classification (1). Currently, the two standard criteria widely used internationally are DSM-IV-TR and ICD-10. According to the DSM-IV-TR criteria, two characteristic symptoms with duration of at least 1 month are required to be met for a complete diagnosis. Characteristic symptoms for schizophrenia include delusion, hallucination, disorganized speech, disorganized behavior/catatonic behavior, and other negative symptoms (2). Exceptions of diagnosis can be made when a patient displays either a bizarre delusion or a hallucination consisting of hearing a running commentary (2). On the contrary, the diagnosis of schizophrenia cannot be made if symptoms of either pervasive developmental disorder or mood disorder are presented (2). The symptoms result of using a substance or of a general medical condition are also excluded from the diagnosis criteria of schizophrenia (2).

6.2 Schizophrenia Subtypes

A patient diagnosed with schizophrenia is assigned with a subtype according to the symptoms of patient experiencing. Both the DSM-IV-TR and ICD-10 define four subtypes of schizophrenia including paranoid, disorganized, catatonic, and undifferentiated2; ICD-10 further categorizes simple schizophrenia and post-schizophrenia depression as the additional subtypes.

Paranoid subtype

Paranoid schizophrenia is the most common subtype of schizophrenia (3). Although positive symptoms such as hallucination or delusion exist, patients diagnosed with paranoid schizophrenia have normal social behaviors and many even have a martial relationship (3). The primary symptoms of paranoid schizophrenia include hallucination and delusion, whereas none of the negative symptoms are present (3). As a result, anti-psychotic medications work the best for this subtype (4). Recent research suggests that the level of endocannabinoid may selectively elevate in the cerebral spinal fluid from post-mortem studies of paranoid schizophrenia patients (3). Moreover, an increase in the cannabinoid receptor, CB1R, in the dorsal lateral prefrontal cortex suggests an involvement of the endocannabinoid system, which is likely responsible for the overall positive symptoms (3). Such CB1R-endocannabinoid system was discovered to be a major target for anti-psychotic substances that alleviates during episodes of positive symptoms (3).

Disorganized subtype

In contrast to paranoid schizophrenia, patients with disorganized (or hebephrenic) schizophrenia have the worst psychotic symptoms presented compare to all other subtype (5). These patients show many negative symptoms that cause them to lose a connection with reality (5). Their speech, cognition, and behavior are all impaired and often inappropriate (5). As a result, patients are not capable of carrying out routine daily activities and often required the aid from social workers, psychiatrists, and family members (6). Disorganized schizophrenia has the worst prognosis; lifelong treatments are often needed with a combination of family therapy and medications (6). Electroconvulsive therapy was newly introduced in recent years; case studies suggest such therapy along without antipsychotic medications can successfully maintain a complete remission for a few years (6).

Catatonic subtype

Catatonic schizophrenia has the most unique and apparent symptoms that makes it a lot easier for an accurate diagnosis by a psychiatrist (7). The hallmark symptoms of patients with catatonic schizophrenia are aberrant physical movements or behaviors (7). Patients often restrict themselves in super slow motion and display awkward postures for a period of time (7). Moreover, they often refuse to engage in a conversation and deny the existence of other individuals (known as negativistic) (7). Patients may also involuntarily mimic a movement or repeat a sentence of others (known as echopraxia and echolalia respectively) (7). Fortunately, with the improved treatment over the past several years, catatonic schizophrenia is rare in our current social community (8).

Undifferentiated subtype

Undifferentiated subtype is used to categorize patients with inconsistent symptoms that do not match the criteria for other subtypes, given that they meet the general criteria for schizophrenia (2). However, there is typically one apparent symptom that triumphs over other symptoms (2).

6.3 Interviewing and assessment

In the psychiatric assessment, structured interviews (or standardized interviews) are most widely used as the standardized approach for the diagnosis of schizophrenia (9). The major advantage is the high reliability by using the DSM-IV-IR to determine the presence of specific symptoms (9). Two primarily assessment instruments include self-report and interview-based that involves rating scales (9). Commonly used rating scales include the Brief Psychiatric Rating Scale (BPRS) or the Positive and Negative Syndrome Scale (PANSS), which are suitable for both the Interview-based and Self-report assessment instruments (9). The scores from the scales are added up overall and summarized to determine the severity of the condition as well as a diagnosis (e.g. either a clear-cut schizophrenia subtype or possible comorbidity) (9).

6.4 Misdiagnosis

It is important that since schizophrenia is a type of psychosis, the psychotic symptoms present in patients with schizophrenia could often result from other conditions or illnesses (2). Psychotic symptoms often require several months or possibly years confirming due to the result of schizophrenia. There are several mental disorders known to have similar symptoms should not be confused to schizophrenia other than brain trauma.

Schizophreniform disorder

The six-month requirement for any psychotic symptoms is critical for a diagnosis for schizophrenia (2). Alternatively, a patient is to be diagnosed with schizophreni-form disorder when he or she experiences these symptoms in a course of at least one but less than six months (2). As a result, schizophreniform disorder can be viewed as the disorder prior to the development full-blown schizophrenia (10).

Brief psychotic disorder

Brief psychotic disorder often refers to symptoms experienced by an individual are sudden and only linger for a few days (2). Such condition is very rare, and psychotic symptoms almost never return after remission (10). The episodes may be triggered by a sudden and extreme stressful event (e.g. death of a close relative or losing a job) (10).

Schizoaffective disorder

It is very common to for individuals with mood disorders also experience the positive and negative symptoms (11). Although some of them may meet the full criteria for schizophrenia, it is important to distinguish them as schizoaffective disorder and not schizophrenia when they experience severe mood swings (11).

Delusional disorder

While individuals with delusional disorder often endorse emotional-consistent delusional beliefs, they typically function normally (12). Beliefs are non-bizarre, emotionally consistent, and do not associate with disorganized or bizarre behavior changes (12). Unlike schizophrenia, delusional disorder usually does not cause hallucinations (12). One famous form of delusion seen in individuals with delusional disorder is erotomania, which an individual has a false belief that he or she is in a love affair with typically a stranger or a famous person (12).

Shared psychotic disorder (induced delusional disorder)

This occurs when a person has a close relationship with another person that has a delusion, and the delusional belief is transmitted to the original person (10).


1. Mas-Exposito L., et al. The World Health Organization Short Disability Assessment Schedule: a validation study in patients with schizophrenia. Comprehensive Psychiatry 2012;53:208-216

2. Schizophrenia and other psychotic disorders. In: Diagnostic and Statistical Manual of Mental Disorders DSM-IV-TR. 4th ed. Arlington, Va.: American Psychiatric Association; 2000.

3. Dalton Victoria S., et al. Paranoid Schizophrenia is Characterized by Increased CB1 Receptor Binding in the Dorsolateral prefrontal cortex. Neuropsychopharmacology. 2011;36:1620-1630.

4. Ho Beng-Choon, et al. Long-term Antipsychotic Treatment and Brain Volumes. Arch Gen Psychiatry. 2011;68(2):128-137.

5. Smith M.J. et al. Self-reported empathy deficits are uniquely associated with poor functioning in schizophrenia. Schizophr. Res. 2012.

6. Kitamura H., et al. Six-year complete remission in a patient with disorganized schizophrenia during maintenance electroconvulsive therapy without antipsychotic medication. Psychiatry and Clinical Neurosciences. 2012;164-5.

7. Rosebush PI, et al. Catatonia and its treatment. Schizophrenia Bulletin. 2010;362:239.

8. Thirthalli J, et al. Does catatonic schizophrenia improve faster with electroconvulsive therapy than other subtypes of schizophrenia? The World Journal of Biological Psychiatry. 2009;10:772.

9. Roe D. and Davidson L. Self and narrative in schizophrenia: Time to author a new story. Journal of Medical Humanities. 2005;31: 89 -94

10. Os J.V., Kapur S. Schizophrenia. Lancet. 2009;374:635-645

11. Fava G.A. and Kellner R., Prodromal Symptoms in Affective Disorders. American Journal of Psychiatry 1991;148:828-830.

12. Wustmann T. et al. The Clinical and Sociodemographic Profile of Persistent Delusional Disorder. Psychopathology 2012;45:200-202