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Schizophrenia and Other Psychotic Disorders
The disorders in this section include Schizophrenia, Schizophreniform Disorder, Schizoaffective Disorder, Delusional Disorder, Brief Psychotic Disorder, Shared Psychotic Disorder, Psychotic Disorder Due to a General Medical Condition, Substance-Induced Psychotic Disorder, and Psychotic Disorder Not Otherwise Specified.
Schizophrenia and Other Psychotic Disorders
These disorders have been grouped together to facilitate the differential diagnosis of disorders that include psychotic symptoms as a prominent aspect of their presentation. Other disorders that may present with psychotic symptoms as associated features are included elsewhere in the manual (e.g., Dementia of the Alzheimer's Type and Substance-Induced Delirium in the "Delirium, Dementia, and Amnestic and Other Cognitive Disorders" section; Major Depressive Disorder, With Psychotic Features, in the "Mood Disorders" section).
Despite the fact that these disorders are grouped together in this section, it should be understood that psychotic symptoms are not necessarily considered to be core or fundamental features of these disorders, nor do the disorders in this section necessarily have a common etiology. In fact, a number of studies suggest closer etiological associations between Schizophrenia and other disorders that, by definition, do not present with psychotic symptoms (e.g., Schizotypal Personality Disorder).
The term psychotic has historically received a number of different definitions, none of which has achieved universal acceptance. The narrowest definition of psychotic is restricted to delusions or prominent hallucinations, with the hallucinations occurring in the absence of insight into their pathological nature. A slightly less restrictive definition would also include prominent hallucinations that the individual realizes are hallucinatory experiences. Broader still is a definition that also includes other positive symptoms of Schizophrenia (i.e., disorganized speech, grossly disorganized or catatonic behavior).
"Several recent studies suggest that frequent cannabis use during adolescence is associated with a clinically significant increased risk of developing schizophrenia and other mental illnesses which feature psychosis.
Some of the headlines about these studies in the media may be leading the everyday reader to believe that there is a direct casual relationship between marijuana and psychosis, i.e. that the average person who smokes some pot may become psychotic. Though this definitely makes for a gripping news story and there are some studies that suggest this causal link, according to the abundance of scientific literature and various other forms of information (e.g. web and print-based resources, anecdotal evidence, documentaries evidence) the nature of the link between the two seems to be more complicated than this."
Feb. 26, 2015 - Schizophrenia Society of Canada
Unlike these definitions based on symptoms, the definition used in earlier classifications (e.g., DSM-II and ICD-9) was probably far too inclusive and focused on the severity of functional impairment. In that context, a mental disorder was termed "psychotic" if it resulted in "impairment that grossly interferes with the capacity to meet ordinary demands of life." The term has also previously been defined as a "loss of ego boundaries" or a "gross impairment in reality testing."
Schizophrenia
A common and serious mental disorder characterized by loss of contact with reality (psychosis), hallucinations (false perceptions), delusions (false beliefs), abnormal thinking
In this manual, the term psychotic refers to the presence of certain symptoms. However, the specific constellation of symptoms to which the term refers varies to some extent across the diagnostic categories. In Schizophrenia, Schizophreniform Disorder, Schizoaffective Disorder, and Brief Psychotic Disorder, the term psychotic refers to delusions, any prominent hallucinations, disorganized speech, or disorganized or catatonic behavior. In Psychotic Disorder Due to a General Medical Condition and in Substance-Induced Psychotic Disorder, psychotic refers to delusions or only those hallucinations that are not accompanied by insight. Finally, in Delusional Disorder and Shared Psychotic Disorder, psychotic is equivalent to delusional.
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The following disorders are included in this section:
Schizophrenia is a disorder that lasts for at least 6 months and includes at least 1 month of active-phase symptoms (i.e., two [or more] of the following: delusions, hallucinations, disorganized speech, grossly disorganized or catatonic behavior, negative symptoms). Definitions for the Schizophrenia subtypes (Paranoid, Disorganized, Catatonic, Undifferentiated, and Residual) are also included in this section.
Schizophreniform Disorder is characterized by a symptomatic presentation that is equivalent to Schizophrenia except for its duration (i.e., the disturbance lasts from 1 to 6 months) and the absence of a requirement that there be a decline in functioning.
Schizoaffective Disorder is a disorder in which a mood episode and the active-phase symptoms of Schizophrenia occur together and were preceded or are followed by at least 2 weeks of delusions or hallucinations without prominent mood symptoms.
Delusional Disorder is characterized by at least 1 month of nonbizarre delusions without other active-phase symptoms of Schizophrenia.
Brief Psychotic Disorder is a disorder that lasts more than 1 day and remits by 1 month.
Shared Psychotic Disorder is characterized by the presence of a delusion in an individual who is influenced by someone else who has a longer-standing delusion with similar content.
In Psychotic Disorder Due to a General Medical Condition, the psychotic symptoms are judged to be a direct physiological consequence of a general medical condition.
In Substance-Induced Psychotic Disorder, the psychotic symptoms are judged to be a direct physiological consequence of a drug of abuse, a medication, or toxin exposure.
Psychotic Disorder Not Otherwise Specified is included for classifying psychotic presentations that do not meet the criteria for any of the specific Psychotic Disorders defined in this section or psychotic symptomatology about which there is inadequate or contradictory information.
Cannabis use and the risk of developing a psychotic disorder
We briefly review the evidence that cannabis use in adolescence and young adulthood is a contributory cause of schizophreniform psychoses, by summarising longitudinal studies that: a) have examined relationships between cannabis use and the risk of psychosis or psychotic symptoms; and b) have controlled for potential confounders, such as other forms of drug use and personal characteristics that predict an increased risk of psychosis. There is now reasonable evidence from longitudinal studies that regular cannabis use predicts an increased risk of schizophrenia and of reporting psychotic symptoms. These relationships have persisted after controlling for confounding variables such as personal characteristics and other drug use. The relationships did not seem to be explained by cannabis being used to self-medicate symptoms of psychosis. A contributory causal relationship is biologically plausible because psychotic disorders involve disturbances in the dopamine neurotransmitter system with which the cannabinoid system interacts, as has been shown by animal studies and a human provocation study. We briefly explore the clinical and public health implications of the most plausible hypothesis, that cannabis use precipitates schizophrenia in persons who are vulnerable because of a personal or family history of schizophrenia.
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Regular cannabis use and psychotic disorders (such as schizophrenia) are associated in the general population, and heavy cannabis users are over-represented among new cases of schizophrenia,. These findings, and rising rates of cannabis use among young people in many developed countries, have prompted debates about whether cannabis use may be a contributory cause of psychosis, that is, it may precipitate schizophrenia in vulnerable individuals. This hypothesis assumes that cannabis use is one factor among many others (including genetic predisposition and other unknown causes) that together cause schizophrenia.
There are also other possible explanations of the association. Common factors may increase the risk of cannabis use and psychosis, without the two being directly related. Cannabis could also be used to self-medicate the symptoms of schizophrenia.
The consistent finding of an association between cannabis use and psychosis makes chance an unlikely explanation of the association, and there are also now a number of prospective studies showing that cannabis use often precedes psychosis. The more difficult task has been excluding the hypothesis that the relationship is due to other factors, such as other drug use or a genetic predisposition to develop schizophrenia and use cannabis.
Marijuana and Psychosis: Which Comes First?
"Carefully conducted prospective studies such as this one provide the best evidence available that cannabis contributes to the cause of some cases of schizophrenia," says Matthew Large of Prince of Wales Hospital in New South Wales, Australia. Large recently published a similar study linking marijuana use to earlier age of onset of schizophrenia.
"The study goes a long way to clarifying that it is not psychosis that causes cannabis use, but rather the reverse," he says in an email.
Tomas Silber, MD, an adolescent medicine doctor at the Children's National Medical Center in Washington, D.C., reviewed the new study for WebMD. He says the new study helps to clarify the relationship between marijuana use and psychotic episodes.
"Marijuana use increases these episodes," he says.
"Many people have suspected that people smoke marijuana as a way of treating themselves, and this study disproves that connection," he says. "It is not a two-way street, it's a one-way street."
SOURCES:
Kuepper, R. BMJ, published online March 1, 2011.
Hall, W. BMJ, published online March 1, 2011.
Matthew Large, Prince of Wales Hospital, New South Wales, Australia.
Tomas Silber, MD, adolescent medicine doctor, Children's National Medical Center.
