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For other uses, see Schizophrenia (disambiguation).
| Schizophrenia Classification & external resources | ||
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|---|---|---|
| Eugen Bleuler (1857–1939) coined the term "Schizophrenia" in 1908 | ||
| ICD-10 | F20. | |
| ICD-9 | 295 | |
| OMIM | 181500 | |
| DiseasesDB | 11890 | |
| MedlinePlus | 000928 | |
| eMedicine | med/2072 emerg/520 | |
| MeSH | F03.700.750 | |
Schizophrenia, from the Greek roots schizein (σχίζειν, "to split") and phrēn, phren- (φρήν, φρεν-, "mind"), is a psychiatric diagnosis that describes a mental illness characterized by impairments in the perception or expression of reality, most commonly manifesting as auditory hallucinations, paranoid or bizarre delusions or disorganized speech and thinking in the context of significant social or occupational dysfunction. Onset of symptoms typically occurs in young adulthood,Castle E; Wessely S, Der G, Murray RM (1991). "The incidence of operationally defined schizophrenia in Camberwell 1965–84". British Journal of Psychiatry 159: 790-794. PMID 1790446. Retrieved on 2008-02-24. with approximately 0.4–0.6%Bhugra, D (2006). "The global prevalence of schizophrenia". PLoS Medicine 2 (5): 372-373. PMID 15916460. Retrieved on 2008-02-24. Goldner EM; Hsu L, Waraich P, Somers JM (2002). "Prevalence and incidence studies of schizophrenic disorders: a systematic review of the literature". Canadian Journal of Psychiatry 47 (9): 833-43. PMID 12500753. Retrieved on 2008-02-24. of the population affected. Diagnosis is based on the patient\'s self-reported experiences and observed behavior. No laboratory test for schizophrenia exists.
Studies suggest that genetics, early environment, neurobiology and psychological and social processes are important contributory factors. Current psychiatric research is focused on the role of neurobiology, but a clear organic cause has not been found. Due to the many possible combinations of symptoms, there is debate about whether the diagnosis represents a single disorder or a number of discrete syndromes. For this reason, Eugen Bleuler termed the disease the schizophrenias (plural) when he coined the name. Despite its etymology, schizophrenia is not synonymous with dissociative identity disorder, previously known as multiple personality disorder or split personality; in popular culture the two are often confused.
Increased dopaminergic activity in the mesolimbic pathway of the brain is a consistent finding. The mainstay of treatment is pharmacotherapy with antipsychotic medications; these primarily work by suppressing dopamine activity. Dosages of antipsychotics are generally lower than in the early decades of their use. Psychotherapy, vocational and social rehabilitation are also important. In more serious cases—where there is risk to self and others—involuntary hospitalization may be necessary, though hospital stays are less frequent and for shorter periods than they were in previous years.Becker T; Kilian R (2006). "Psychiatric services for people with severe mental illness across western Europe: what can be generalized from current knowledge about differences in provision, costs and outcomes of mental health care?". Acta Psychiatrica Scandinavica Supplement 429: 9-16. PMID 16445476. Retrieved on 2008-02-24.
The disorder is primarily thought to affect cognition, but it also usually contributes to chronic problems with behavior and emotion. People diagnosed with schizophrenia are likely to be diagnosed with comorbid conditions, including clinical depression and anxiety disorders; the lifetime prevalence of substance abuse is typically around 40%. Social problems, such as long-term unemployment, poverty and homelessness, are common and life expectancy is decreased; the average life expectancy of people with the disorder is 10 to 12 years less than those without, owing to increased physical health problems and a high suicide rate.Brown S; Inskip H, Barraclough B (2000). "Causes of the excess mortality of schizophrenia". Br J Psychiatry 177: 212-7. PMID 11040880. Retrieved on 2008-02-24.
Contents |
A person experiencing schizophrenia may demonstrate symptoms such as disorganized thinking, auditory hallucinations, and delusions. In severe cases, the person may be largely mute, remain motionless in bizarre postures, or exhibit purposeless agitation; these are signs of catatonia. The current classification of psychoses holds that symptoms need to have been present for at least one month in a period of at least six months of disturbed functioning. A schizophrenia-like psychosis of shorter duration is termed a schizophreniform disorder.American Psychiatric Association (2004) Diagnostic and Statistical Manual of Mental Disorders DSM-IV-TR (Text Revision). American Psychiatric Association. ISBN 0890420246. DSM-IV & DSM-IV-TR Schizophrenia criteria No one sign is diagnostic of schizophrenia, and all can occur in other medical and psychiatric conditions.
Social isolation commonly occurs and may be due to a number of factors. Impairment in social cognition is associated with schizophrenia, as are the active symptoms of paranoia from delusions and hallucinations, and the negative symptoms of apathy and avolition. Many people diagnosed with schizophrenia avoid potentially stressful social situations that may exacerbate mental distress.Freeman D; Garety PA, Kuipers E, Fowler D, Bebbington PE, Dunn G (2007). "Acting on persecutory delusions: the importance of safety seeking". Behaviour Research and Therapy 45 (1): 89-99. PMID 16530161. Retrieved on 2008-02-24.
Late adolescence and early adulthood are peak years for the onset of schizophrenia. These are critical periods in a young adult\'s social and vocational development, and they can be severely disrupted by disease onset. To minimize the effect of schizophrenia, much work has recently been done to identify and treat the prodromal (pre-onset) phase of the illness, which has been detected up to 30 months before the onset of symptoms, but may be present longer.Addington J; Cadenhead KS, Cannon TD, Cornblatt B, McGlashan TH, Perkins DO, Seidman LJ, Tsuang M, Walker EF, Woods SW, Heinssen R (2007). "North American prodrome longitudinal study: a collaborative multisite approach to prodromal schizophrenia research". Schizophrenia Bulletin 33 (3): 665-72. PMID 17255119. Retrieved on 2008-02-24. Those who go on to develop schizophrenia may experience the non-specific symptoms of social withdrawal, irritability and dysphoria in the prodromal period,Parnas J; Jorgensen A (1989). "Pre-morbid psychopathology in schizophrenia spectrum". British Journal of Psychiatry 115: 623-7. PMID 2611591. Retrieved on 2008-02-24. and transient or self-limiting psychotic symptoms in the prodromal phase before psychosis becomes apparent.Amminger GP; Leicester S, Yung AR, Phillips LJ, Berger GE, Francey SM, Yuen HP, McGorry PD (2006). "Early-onset of symptoms predicts conversion to non-affective psychosis in ultra-high risk individuals". Schizophrenia Research 84 (1): 67-76. PMID 16677803. Retrieved on 2008-02-24.
The psychiatrist Kurt Schneider (1887–1967) listed the forms of psychotic symptoms that he thought distinguished schizophrenia from other psychotic disorders. These are called first-rank symptoms or Schneider\'s first-rank symptoms, and they include delusions of being controlled by an external force; the belief that thoughts are being inserted into or withdrawn from one\'s conscious mind; the belief that one\'s thoughts are being broadcast to other people; and hearing hallucinatory voices that comment on one\'s thoughts or actions or that have a conversation with other hallucinated voices.Schneider, K. (1959) Clinical Psychopathology. New York: Grune and Stratton. The reliability of first-rank symptoms has been questioned,Bertelsen, A (2002). "Schizophrenia and Related Disorders: Experience with Current Diagnostic Systems". Psychopathology 35: 89-93. PMID 12145490. Retrieved on 2008-02-24. although they have contributed to the current diagnostic criteria.
Schizophrenia is often described in terms of positive (or productive) and negative (or deficit) symptoms.Sims A (2002) Symptoms in the Mind: An Introduction to Descriptive Psychopathology (3rd edition). Edinburgh: Elsevier Science Ltd. ISBN 0-7020-2627-1 Positive symptoms include delusions, auditory hallucinations, and thought disorder, and are typically regarded as manifestations of psychosis. Negative symptoms are so-named because they are considered to be the loss or absence of normal traits or abilities, and include features such as flat or blunted affect and emotion, poverty of speech (alogia), anhedonia, and lack of motivation (avolition). Despite the appearance of blunted affect, recent studies indicate that there is often a normal or even heightened level of emotionality in Schizophrenia especially in response to stressful or negative events.Cohen & Docherty (2004). "Affective reactivity of speech and emotional experience in patients with schizophrenia". Schizophrenia Research 69 (1): 7-14. PMID 15145465. Retrieved on 2008-02-24. A third symptom grouping, the disorganization syndrome, is commonly described, and includes chaotic speech, thought, and behaviour. There is evidence for a number of other symptom classifications.Peralta V; Cuesta MJ (2001). "How many and which are the psychopathological dimensions in schizophrenia? Issues influencing their ascertainment". Schizophrenia Research 49 (3): 269-85. PMID 11356588. Retrieved on 2008-02-24.
Diagnosis is based on the self-reported experiences of the person as well as abnormalities in behavior reported by family members, friends or co-workers, followed by secondary signs observed by a psychiatrist, social worker, clinical psychologist or other clinician in a clinical assessment. There is a list of criteria that must be met for someone to be so diagnosed. These depend on both the presence and duration of certain signs and symptoms.
An initial assessment includes a comprehensive history and physical examination by a physician. Although there are no biological tests which confirm schizophrenia, tests are carried out to exclude medical illnesses which may rarely present with psychotic schizophrenia-like symptoms. These include blood tests measuring TSH to exclude hypo- or hyperthyroidism, basic electrolytes and serum calcium to rule out a metabolic disturbance, full blood count including ESR to rule out a systemic infection or chronic disease, and serology to exclude syphilis or HIV infection; two commonly ordered investigations are EEG to exclude epilepsy, and a CT scan of the head to exclude brain lesions. It is important to rule out a delirium which can be distinguished by visual hallucinations, acute onset and fluctuating level of consciousness and indicates an underlying medical illness. There are several psychiatric illnesses which may present with psychotic symptoms other than schizophrenia. These include bipolar disorder,Pope HG (1983). "Distinguishing bipolar disorder from schizophrenia in clinical practice: guidelines and case reports". Hospital and Community Psychiatry 34: 322-328. Retrieved on 2008-02-24. borderline personality disorder,McGlashan TH (1987) Testing DSM-III symptom criteria for schizotypal and borderline personality disorders. Archives of General Psychiatry, 44: 15–22. drug intoxication, brief drug-induced psychosis, and schizophreniform disorder.
Investigations are not generally repeated for relapse unless there is a specific medical indication. These may include serum blood sugar level (BSL) if olanzapine has been prescribed previously, liver function tests if chlorpromazine, or creatine phosphokinase (CPK) to exclude neuroleptic malignant syndrome. Assessment and treatment are usually done on an outpatient basis; admission to an inpatient facility is considered if there is a risk to self or others.
The most widely used criteria for diagnosing schizophrenia are from the American Psychiatric Association\'s Diagnostic and Statistical Manual of Mental Disorders, the current version being DSM-IV-TR, and the World Health Organization\'s International Statistical Classification of Diseases and Related Health Problems, currently the ICD-10. The latter criteria are typically used in European countries while the DSM criteria are used in the USA or the rest of the world, as well as prevailing in research studies. The ICD-10 criteria put more emphasis on Schneiderian first rank symptoms although, in practice, agreement between the two systems is high.Jakobsen KD; Frederiksen JN, Hansen T, Jansson LB, Parnas J, Werge T (2005). "Reliability of clinical ICD-10 schizophrenia diagnoses". Nordic Journal of Psychiatry 59 (3): 209-12. PMID 16195122. Retrieved on 2008-02-24. The WHO has developed the tool SCAN (Schedules for Clinical Assessment in Neuropsychiatry) which can be used for diagnosing a number of psychiatric conditions, including schizophrenia.
To be diagnosed with schizophrenia, a person must display:
Additional criteria are also given that exclude the diagnosis; thus schizophrenia cannot be diagnosed if symptoms of mood disorder or pervasive developmental disorder are present, or the symptoms are the direct result of a substance (e.g., abuse of a drug/medication) or a general medical condition.
Historically, schizophrenia in the West was classified into simple, catatonic, hebephrenic (now known as disorganized), and paranoid. The DSM contains five sub-classifications of schizophrenia:
The ICD-10 recognises a further two subtypes:
Schizophrenia as a diagnostic entity has been criticised as lacking in scientific validity or reliability,Bentall RP (1992) Reconstructing Schizophrenia. London: Routledge. ISBN 0415075246Boyle M (2002) Schizophrenia: A Scientific Delusion?. London: Routledge. ISBN 0415227186 part of a larger criticism of the validity of psychiatric diagnoses in general. One alternative suggests that the issues with the diagnosis would be better addressed as individual dimensions along which everyone varies, such that there is a spectrum or continuum rather than a cut-off between normal and ill. This approach appears consistent with research on schizotypy and of a relatively high prevalence of psychotic experiencesVerdoux H; van Os J (2002). "Psychotic symptoms in non-clinical populations and the continuum of psychosis". Schizophrenia Research 54 (1-2): 59-65. PMID 11853979. Retrieved on 2008-02-24. Johns LC; van Os J (2001). "The continuity of psychotic experiences in the general population". Clinical Psychology Review 21 (8): 1125-41. PMID 11702510. Retrieved on 2008-02-24. and often non-distressing delusional beliefsPeters ER; Day S, McKenna J, Orbach G (2005). "Measuring delusional ideation: the 21-item Peters et al. Delusions Inventory (PDI)". Schizophrenia Bulletin 30: 1005-22. PMID 15954204. Retrieved on 2008-02-24. amongst the general public.
Another criticism is that the definitions used for criteria lack consistency;David AS (1999). "On the impossibility of defining delusions". Philosophy, Psychiatry and Psychology 6 (1): 17-20. Retrieved on 2008-02-24. this is particularly relevant to the evaluation of delusions and thought disorder. More recently, it has been argued that psychotic symptoms are not a good basis for making a diagnosis of schizophrenia as "psychosis is the \'fever\' of mental illness — a serious but nonspecific indicator".Tsuang MT; Stone WS, Faraone SV (2000). "Toward reformulating the diagnosis of schizophrenia". American Journal of Psychiatry 157 (7): 1041-1050. PMID 10873908. Retrieved on 2008-02-24.
Perhaps because of these factors, studies examining the diagnosis of schizophrenia have typically shown relatively low or inconsistent levels of diagnostic reliability. Most famously, David Rosenhan\'s 1972 study, published as On being sane in insane places, demonstrated that the diagnosis of schizophrenia was (at least at the time) often subjective and unreliable.Rosenhan D (1973). "On being sane in insane places". Science 179: 250-8. PMID 4683124. Retrieved on 2008-02-24. More recent studies have found agreement between any two psychiatrists when diagnosing schizophrenia tends to reach about 65% at best.McGorry PD; Mihalopoulos C, Henry L, Dakis J, Jackson HJ, Flaum M, Harrigan S, McKenzie D, Kulkarni J, Karoly R (1995). "Spurious precision: procedural validity of diagnostic assessment in psychotic disorders". American Journal of Psychiatry 152 (2): 220-3. PMID 7840355. Retrieved on 2008-02-24. This, and the results of earlier studies of diagnostic reliability (which typically reported even lower levels of agreement) have led some critics to argue that the diagnosis of schizophrenia should be abandoned.Read J (2004) Does \'schizophrenia\' exist? Reliability and validity. In Read J, Mosher LR, Bentall RP (eds) Models of Madness: Psychological, Social and Biological Approaches to Schizophrenia. ISBN 1-58391-906-6
In 2004 in Japan, the Japanese term for schizophrenia was changed from Seishin-Bunretsu-Byo (mind-split-disease) to Tōgō-shitchō-shō (integration disorder).Sato M (2004). "Renaming schizophrenia: a Japanese perspective". World Psychiatry 5 (1): 53-5. PMID 16757998. Retrieved on 2008-02-24. In 2006, campaigners in the UK, under the banner of Campaign for Abolition of the Schizophrenia Label, argued for a similar rejection of the diagnosis of schizophrenia and a different approach to the treatment and understanding of the symptoms currently associated with it.Schizophrenia term use \'invalid\'. BBC News Online, (9 October 2006). Retrieved on 2007-05-16.
Alternatively, other proponents have put forward using the presence of specific neurocognitive deficits to make a diagnosis. These take the form of a reduction or impairment in basic psychological functions such as memory, attention, executive function and problem solving. It is these sorts of difficulties, rather than the psychotic symptoms (which can in many cases be controlled by antipsychotic medication), which seem to be the cause of most disability in schizophrenia. However, this argument is relatively new and it is unlikely that the method of diagnosing schizophrenia will change radically in the near future.Green MF (2001) Schizophrenia Revealed: From Neurons to Social Interactions. New York: W.W. Norton. ISBN 0393703347
The diagnosis of schizophrenia has been used for political rather than therapeutic purposes; in the Soviet Union an additional sub-classification of sluggishly progressing schizophrenia was created. Particularly in the RSFSR (Russian Soviet Federated Socialist Republic), this diagnosis was used for the purpose of silencing political dissidents or forcing them to recant their ideas by the use of forcible confinement and treatment.Wilkinson G (1986). "Political dissent and "sluggish" schizophrenia in the Soviet Union". Br Med J (Clin Res Ed) 293 (6548): 641-2. PMID 3092963. Retrieved on 2008-02-24. In 2000 there were similar concerns regarding detention and \'treatment\' of practitioners of the Falun Gong movement by the Chinese government. This led the American Psychiatric Association\'s Committee on the Abuse of Psychiatry and Psychiatrists to pass a resolution to urge the World Psychiatric Association to investigate the situation in China.Lyons D (2001). "Soviet-style psychiatry is alive and well in the People\'s Republic". British Journal of Psychiatry 178: 380-381. PMID 11282823. Retrieved on 2008-02-24.
Schizophrenia occurs equally in males and females although typically appears earlier in men with the peak ages of onset being 20–28 years for males and 26–32 years for females. Much rarer are instances of childhood-onsetKumra S; Shaw M, Merka P, Nakayama E, Augustin R (2001). "Childhood-onset schizophrenia: research update". Canadian Journal of Psychiatry 46 (10): 923-30. PMID 11816313. Retrieved on 2008-02-24. and late- (middle age) or very-late-onset (old age) schizophrenia.Hassett A, Ames D, Chiu E (eds) (2005) Psychosis in the Elderly. London: Taylor and Francis. ISBN 18418439446 The lifetime prevalence of schizophrenia, that is, the proportion of individuals expected to experience the disease at any time in their lives, is commonly given at 1%. A 2002 systematic review of many studies, however, found a lifetime prevalence of 0.55%. Despite the received wisdom that schizophrenia occurs at similar rates throughout the world, its prevalence varies across the world,Jablensky A; Sartorius N, Ernberg G, Anker M, Korten A, Cooper JE, Day R, Bertelsen A (1992). "Schizophrenia: manifestations, incidence and course in different cultures. A World Health Organization ten-country study". Psychological Medicine Monograph Supplement 20: 1-97. PMID 1565705. Retrieved on 2008-02-24. within countries,Kirkbride JB; Fearon P, Morgan C, Dazzan P, Morgan K, Tarrant J, Lloyd T, Holloway J, Hutchinson G, Leff JP, Mallett RM, Harrison GL, Murray RM, Jones PB (2006). "Heterogeneity in incidence rates of schizophrenia and other psychotic syndromes: findings From the 3-center ÆSOP study". Archives of General Psychiatry 63 (3): 250-258. PMID 16520429. Retrieved on 2008-02-24. and at the local and neighbourhood level.Kirkbride JB; Fearon P, Morgan C, Dazzan P, Morgan K, Murray RM, Jones PB (2007). "Neighbourhood variation in the incidence of psychotic disorders in Southeast London". Social Psychiatry and Psychiatric Epidemiology 42 (6): 438-45. PMID 17473901. Retrieved on 2008-02-24. One particularly stable and replicable finding has been the association between living in an urban environment and schizophrenia diagnosis, even after factors such as drug use, ethnic group and size of social group have been controlled for.Van Os J (2004). "Does the urban environment cause psychosis?". British Journal of Psychiatry 184 (4): 287-288. PMID 15056569. Retrieved on 2008-02-24. Schizophrenia is known to be a major cause of disability. In a 1999 study of 14 countries, active psychosis was ranked the third-most-disabling condition, after quadriplegia and dementia and before paraplegia and blindness.Ustun TB; Rehm J, Chatterji S, Saxena S, Trotter R, Room R, Bickenbach J, and the WHO/NIH Joint Project CAR Study Group (1999). "Multiple-informant ranking of the disabling effects of different health conditions in 14 countries". The Lancet 354 (9173): 111-115. PMID 10408486. Retrieved on 2008-02-24.
Data from a PET studyMeyer-Lindenberg A; Miletich RS, Kohn PD, Esposito G, Carson RE, Quarantelli M, Weinberger DR, Berman KF (2002). "Reduced prefrontal activity predicts exaggerated striatal dopaminergic function in schizophrenia". Nature Neuroscience 5: 267-71. PMID 11865311. Retrieved on 2008-02-24. suggests that the less the frontal lobes are activated (red) during a working memory task, the greater the increase in abnormal dopamine activity in the striatum (green), thought to be related to the neurocognitive deficits in schizophrenia.
While the reliability of the diagnosis introduces difficulties in measuring the relative effect of genes and environment (for example, symptoms overlap to some extent with severe bipolar disorder or major depression), evidence suggests that genetic and environmental factors can act in combination to result in schizophrenia.Harrison PJ; Owen MJ (2003). "Genes for schizophrenia? Recent findings and their pathophysiological implications". The Lancet 361 (9355): 417-9. PMID 12573388. Retrieved on 2008-02-24. Evidence suggests that the diagnosis of schizophrenia has a significant heritable component but that onset is significantly influenced by environmental factors or stressors.Day R; Nielsen JA, Korten A, Ernberg G, Dube KC, Gebhart J, Jablensky A, Leon C, Marsella A, Olatawura M, et al. (1987). "Stressful life events preceding the acute onset of schizophrenia: a cross-national study from the World Health Organization". Culture, Medicine and Psychiatry 11 (2): 123-205. PMID 3595169. Retrieved on 2008-02-24. The idea of an inherent vulnerability (or diathesis) in some people, which can be unmasked by biological, psychological or environmental stressors, is known as the stress-diathesis model.Corcoran C; Walker E, Huot R, Mittal V, Tessner K, Kestler L, Malaspina D (2003). "The stress cascade and schizophrenia: etiology and onset". Schizophrenia Bulletin 29 (4): 671-92. PMID 14989406. Retrieved on 2008-02-24. The idea that biological, psychological and social factors are all important is known as the "biopsychosocial" model.
Estimates of the heritability of schizophrenia tend to vary owing to the difficulty of separating the effects of genetics and the environment although twin studies have suggested a high level of heritability.O\'Donovan MC; Williams NM, Owen MJ (2003). "Recent advances in the genetics of schizophrenia". Human Molecular Genetics 12 Spec No 2: R125-33. PMID 12952866. Retrieved on 2008-02-24. It is likely that schizophrenia is a condition of complex inheritance, with several genes possibly interacting to generate risk for schizophrenia or the separate components that can co-occur leading to a diagnosis.Owen MJ; Craddock N, O\'Donovan MC (2005). "Schizophrenia: genes at last?". Trends in Genetics 21 (9): 518-25. PMID 16009449. Retrieved on 2008-02-24. Recent work has suggested that genes that raise the risk for developing schizophrenia are non-specific, and may also raise the risk of developing other psychotic disorders such as bipolar disorder.Craddock N; O\'Donovan MC, Owen MJ (2006). "Genes for schizophrenia and bipolar disorder? Implications for psychiatric nosology". Schizophrenia Bulletin 32 (1): 9-16. PMID 16319375. Retrieved on 2008-02-24. Dalby JT; Morgan D, Lee M (1986). "Schizophrenia and mania in identical twin brothers". Journal of Nervous and Mental Disease 174: 304-308. PMID 3701318. Retrieved on 2008-02-24.
It is thought that causal factors can initially come together in early neurodevelopment, including during pregnancy, to increase the risk of later developing schizophrenia. One curious finding is that people diagnosed with schizophrenia are more likely to have been born in winter or spring, (at least in the northern hemisphere).Davies G; Welham J, Chant D, Torrey EF, McGrath J (2003). "A systematic review and meta-analysis of Northern Hemisphere season of birth studies in schizophrenia". Schizophrenia Bulletin 29 (3): 587-93. PMID 14609251. Retrieved on 2008-02-24. There is now evidence that prenatal exposure to infections increases the risk for developing schizophrenia later in life, providing additional evidence for a link between in utero developmental pathology and risk of developing the condition.Brown AS (2006). "Prenatal infection as a risk factor for schizophrenia". Schizophrenia Bulletin 32 (2): 200-2. PMID 16469941. Retrieved on 2008-02-24.
Living in an urban environment has been consistently found to be a risk factor for schizophrenia.van Os J; Krabbendam L, Myin-Germeys I, Delespaul P (2005). "The schizophrenia envirome". Current Opinion in Psychiatry 18 (2): 141-5. PMID 16639166. Retrieved on 2008-02-24. Social disadvantage has been found to be a risk factor, including povertyMueser KT & McGurk SR (2004). "Schizophrenia". The Lancet 363 (9426): 2063-72. PMID 15207959. Retrieved on 2008-02-24. and migration related to social adversity, racial discrimination, family dysfunction, unemployment or poor housing conditions. (2007) "Migration and schizophrenia". Current Opinion in Psychiatry 20 (2): 111-5. PMID 17278906. Retrieved on 2008-02-24. Childhood experiences of abuse or trauma have also been implicated as risk factors for a diagnosis of schizophrenia later in life.Schenkel LS; Spaulding WD, Dilillo D, Silverstein SM (2005). "Histories of childhood maltreatment in schizophrenia: Relationships with premorbid functioning, symptomatology, and cognitive deficits". Schizophrenia Research 76 (2-3): 273-286. PMID 15949659. Retrieved on 2008-02-24. Janssen; Krabbendam L, Bak M, Hanssen M, Vollebergh W, de Graaf R, van Os J (2004). "Childhood abuse as a risk factor for psychotic experiences". Acta Psychiatrica Scandinavica 109: 38-45. PMID 14674957. Retrieved on 2008-02-24. Parenting is not held responsible for schizophrenia but unsupportive dysfunctional relationships may contribute to an increased risk.Subotnik, KL; Goldstein, MJ, Nuechterlein, KH, Woo, SM and Mintz, J (2002). "Are Communication Deviance and Expressed Emotion Related to Family History of Psychiatric Disorders in Schizophrenia?". Schizophrenia Bulletin 28 (4): 719-29. PMID 12795501. Retrieved on 2008-02-24.
The relationship between schizophrenia and drug use is complex, meaning that a clear causal connection between drug use and schizophrenia has been difficult to distinguish. There is strong evidence that using certain drugs can trigger either the onset or relapse of schizophrenia in some people. It may also be the case, however, that people with schizophrenia use drugs to overcome negative feelings associated with both the commonly prescribed antipsychotic medication and the condition itself, where negative emotion, paranoia and anhedonia are all considered to be core features.Gregg L; Barrowclough C, Haddock G (2007). "Reasons for increased substance use in psychosis". Clinical Psychology Review 27 (4): 494-510. PMID 17240501. Retrieved on 2008-02-24. Amphetamines trigger the release of dopamine and excessive dopamine function is believed to be responsible for many symptoms of schizophrenia (known as the dopamine hypothesis of schizophrenia), amphetamines may worsen schizophrenia symptoms.Laruelle M; Abi-Dargham A, van Dyck CH, Gil R, D\'Souza CD, Erdos J, McCance E, Rosenblatt W, Fingado C, Zoghbi SS, Baldwin RM, Seibyl JP, Krystal JH, Charney DS, Innis RB (1996). "Single photon emission computerized tomography imaging of amphetamine-induced dopamine release in drug-free schizophrenic subjects". Proceedings of the National Academy of Sciences of the USA 93: 9235-40. PMID 8799184. Retrieved on 2008-02-24. Schizophrenia can be triggered by heavy use of hallucinogenic or stimulant drugs.Mueser KT; Yarnold PR, Levinson DF, Singh H, Bellack AS, Kee K, Morrison RL, Yadalam KG (1990). "Prevalence of substance abuse in schizophrenia: demographic and clinical correlates". Schizophrenic Bulletin 16 (1): 31-56. PMID 2333480. Retrieved on 2008-02-24. One study suggests that cannabis use can contribute to psychosis, though the researchers suspected cannabis use was only a small component in a broad range of factors that can cause psychosis.Arseneault L; Cannon M, Witton J, Murray RM (2004). "Causal association between cannabis and psychosis: examination of the evidence". British Journal of Psychiatry 184: 110-7. PMID 14754822. Retrieved on 2008-02-24.
A number of psychological mechanisms have been implicated in the development and maintenance of schizophrenia. Cognitive biases that have been identified in those with a diagnosis or those at risk, especially when under stress or in confusing situations, include excessive attention to potential threats, jumping to conclusions, making external attributions, impaired reasoning about social situations and mental states, difficulty distinguishing inner speech from speech from an external source, and difficulties with early visual processing and maintaining concentration.Broome MR; Woolley JB, Tabraham P, Johns LC, Bramon E, Murray GK, Pariante C, McGuire PK, Murray RM (2005). "What causes the onset of psychosis?". Schizophrenia Research 79 (1): 23-34. PMID 16198238. Retrieved on 2008-02-26. Lewis R (2004). "Should cognitive deficit be a diagnostic criterion for schizophrenia?". Journal of Psychiatry and Neuroscience 29 (2): 102-113. PMID 15069464. Retrieved on 2008-02-26. Brune M; Abdel-Hamid M, Lehmkamper C, Sonntag C (2007). "Mental state attribution, neurocognitive functioning, and psychopathology: What predicts poor social competence in schizophrenia best?". Schizophrenia Research 92 (1-2): 151-9. PMID 17346931. Retrieved on 2008-02-26. Sitskoorn MM; Aleman A, Ebisch SJH, Appels MCM, Khan RS (2004). "Cognitive deficits in relatives of patients with schizophrenia: a meta-analysis". Schizophrenia Research 71 (2): 285-295. PMID 15474899. Retrieved on 2008-02-26. Some cognitive features may reflect global neurocognitive deficits in memory, attention, problem-solving, executive function or social cognition, while others may be related to particular issues and experiences.Kurtz MM (2005). "Neurocognitive impairment across the lifespan in schizophrenia: an update". Schizophrenia Research 74 (1): 15-26. PMID 15694750. Retrieved on 2008-02-26. Bentall RP; Fernyhough C, Morrison AP, Lewis S, Corcoran R (2007). "Prospects for a cognitive-developmental account of psychotic experiences". Br J Clin Psychol 46 (Pt 2): 155-73. PMID 17524210. Retrieved on 2008-02-26. Despite a common appearance of "blunted affect", recent findings indicate that many individuals diagnosed with schizophrenia are highly emotionally responsive, particularly to stressful or negative stimuli, and that such sensitivity may cause vulnerability to symptoms or to the disorder.Cohen & Docherty (2004). "Affective reactivity of speech and emotional experience in patients with schizophrenia". Schizophrenia Research 69 (1): 7-14. PMID 15145465. Retrieved on 2008-02-26. Horan WP; Blanchard JJ (2003). "Emotional responses to psychosocial stress in schizophrenia: the role of individual differences in affective traits and coping". Schizophrenia Research 60 (2-3): 271-83. PMID 12591589. Retrieved on 2008-02-26. Barrowclough C; Tarrier N, Humphreys L, Ward J, Gregg L, Andrews B (2003). "Self-esteem in schizophrenia: relationships between self-evaluation, family attitudes, and symptomatology". J Abnorm Psychol 112 (1): 92-9. PMID 12653417. Retrieved on 2008-02-26. Some evidence suggests that the content of delusional beliefs and psychotic experiences can reflect emotional causes of the disorder, and that how a person interprets such experiences can influence symptomology.Birchwood M; Meaden A, Trower P, Gilbert P, Plaistow J (2000). "The power and omnipotence of voices: subordination and entrapment by voices and significant others". Psychol Med 30 (2): 337-44. PMID 10824654. Retrieved on 2008-02-26. Smith B; Fowler DG, Freeman D, Bebbington P, Bashforth H, Garety P, Dunn G, Kuipers E (2006). "Emotion and psychosis: links between depression, self-esteem, negative schematic beliefs and delusions and hallucinations". Schizophrenia Research 86 (1-3): 181-8. PMID 16857346. Retrieved on 2008-02-26. Beck, AT (2004). "A Cognitive Model of Schizophrenia". Journal of Cognitive Psychotherapy 18 (3): 281-88. Retrieved on 2007-05-16. Bell V; Halligan PW, Ellis HD (2006). "Explaining delusions: a cognitive perspective". Trends in Cognitive Science 10 (5): 219-26. PMID 16600666. Retrieved on 2008-02-26. Further evidence for the role of psychological mechanisms comes from the effects of therapies on symptoms of schizophrenia.Kuipers E; Garety P, Fowler D, Freeman D, Dunn G, Bebbington P (2006). "Cognitive, emotional, and social processes in psychosis: refining cognitive behavioral therapy for persistent positive symptoms". Schizophrenia Bulletin 32 (Suppl 1): S24-31. PMID 16885206. Retrieved on 2008-02-26.
Functional magnetic resonance imaging and other brain imaging technologies allow for the study of differences in brain activity among people diagnosed with schizophrenia.
Studies using neuropsychological tests and brain imaging technologies such as fMRI and
