Schizophrenia and Obsessive Compulsive Disorder

VOLUME 5, NUMBERS 3-4, DECEMBER 2011 27

ABSTRACT:The presence of obsessive-compulsive symptoms

(OCS) or obsessive-compulsive disorder (OCD) is com-mon in patients with schizophrenia. The impact of OCSand OCD on the severity of psychotic symptoms has beenassessed in several studies. There is growing evidence thatpatients with comorbid obsessivecompulsive disorder(OCD) and schizophrenia may represent a special catego-ry of the schizophrenia population. Contemporary inves-tigators contend that there may be a specific pattern ofneurobiologic dysfunction in this subgroup of patients thataccounts for symptom co-expression. Accurate diagnosisis important, given that current treatments for OCD andschizophrenia differ and the choice of diagnosis made hasprognostic implications.

Key Words: obsessive-compulsive disorder, schizo-phrenia, comorbidity

REZUMAT:Prezena simptomelor obsesiv-compulsive este

comun la pacienii cu schizofrenie. Impactul OCS iOCD asupra severitii simptomelor psihotice a fostprezentat n diferite studii. Exist tot mai multe dovezi caresusin c pacienii cu schizofrenie i tulburare obsesivcompulsiv ar putea reprezenta o categorie special.Studiile arat c ar putea exista un model specific de dis-funcie neurobiologic la acest subgrup de pacieni, care sdetermine co-expresia simptomelor. Un diagnostic corecteste important, deoarece tratamentele pentru OCD i pen-tru schizofrenie sunt diferite, iar diagnosticul ales are iimplicaii asupra prognosticului.

Cuvinte cheie: tulburare obsesiv compulsiv,schizofrenie, comorbiditi.

INTRODUCTION

Schizophrenic patients may have obsessive-compul-sive (OC) symptoms and patients that have obsessive-

compulsive disorder (OCD) may have psychotic symp-toms. The lifetime comorbidity rate of schizophrenia andOCD was reported to be higher than the individual lifetimeprevalence rate of each disorder and, therefore, researcherssuggest that there might be a psychopathological relation-ship between schizophrenia and OCD. Both disorders haveearly age onsets. Both disorders have a chronic course andaffect males and females similarly. Both disorders arecharacterized by disturbing thoughts and bizarre behav-iour. A growing literature suggests that obsessive-compul-sive symptoms (OCS) and obsessive-compulsive disorder(OCD) occur in a higher proportion of patients with schiz-ophrenia than was originally suspected .There is a com-mon assumption that both disorders affect the sameanatomical pathways, and that afferent impulses are notfiltered adequately by the thalamus. Although the neurobi-ological basis of schizophrenia and OCD have beenexplained with comparative studies and despite all sup-portive epidemiological and biological findings, the rela-tionship between OCD and schizophrenia is not wellunderstood (Glcan et al., 2008, Kumbhani et al. 2010 ).

COMORBIDITY BETWEEN SCHIZOPHRENIAAND OBSESSIVE-COMPULSIVE DISORDER

Co-occurrence of obsessivecompulsive symptoms(OCS) and psychotic illness was first recognized over acentury ago (Bottas et al. 2005). Early descriptions ofobsessive-compulsive symptoms in schizophrenia can befound in Bleulers monography on dementia praecox.compulsive thinking (obsession) is the most common ofall the automatic phenomena, Bleuler stated, and furtherdescribed OCS in schizophrenia as automatisms, whichare comparable to auditory or visual hallucinations in thatthey are hallucinations of thinking, striving, and wanting. Confirming these observations, case reports and largersystematic studies have since suggested that more than athird of the persons with schizophrenia experience clini-

Schizophrenia and obsessive-compulsive disorder

DENISA-OANA CLIN1, TEFANIA TOT-BORNESCU1, SIMONA MACOVEI2

1 Resident physician in Child and Adolescent Psychiatry, Child and Adolescent Psychiatry Department, Prof. Dr. Al. Obregia Hospital of Psychiatry,Bucharest2 MD, Primary doctor in Child and Adolescent Psychiatry, Child and Adolescent Psychiatry Department, Prof. Dr. Al. Obregia Psychiatry Hospital,Bucharest, Assistant Professor Child and Adolescent Psychiatry Department, University of Medicine and Pharmacy Carol Davila Bucharest, Romania

VOLUME 5, NUMBERS 3-4, DECEMBER 2011

D.-O. CLIN, T. TOT-BORNESCU, S. MACOVEI

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cally significant OCS, while roughly 10% to 25% meet fulldiagnostic criteria for obsessive compulsive disorder(OCD) (Lysaker et al. 2009). Many patients with schizo-phrenia can distinguish the egodystonic OC symptoms,perceived as coming from within, from the egosyntonicdelusions perceived as intruding from the outside. Follow-up studies demonstrate diagnostic stability over time and itseems that the presence of OCD in schizophrenia predictsa poor prognosis. The presence of OCD or significant OCSin patients with schizophrenia has been associated withmore severe psychosis and depression, poorer social func-tioning, lesser likelihood of being employed, and poorerprognosis. Due to the different (poorer) prognosis ofpatients with schizo-obsessive symptoms, as well as pre-liminary data regarding their response to specific therapeu-tic intervention (i.e., the combination of antipsychotic andantiobsessive medications), and taking into account thehigh prevalence of this presentation, several researchershave suggested that a schizo-obsessive category may beconsidered. Schizophrenia patients with concurrent OCSconstitute an intriguing subgroup of individuals. Threemain types of interrelation between OCS and psychoticdisorder are described: 1) those whose OCS are independ-ent from psychosis; 2) those whose OCS are partially relat-ed to their psychosis; and 3) those whose OCS represent acontinuum of their psychosis. Clinically and anamnestical-ly, we are able to distinguish three main subgroups ofpatients: 1) those who met the DSM-IV criteria for OCDbefore the development of schizophrenic process; 2) thosewho began to exhibit OC symptoms around the onset (i.e.in prodromal phase) or at any time during the course ofschizophrenia; and 3) schizophrenic patients having tran-sient OC symptoms on different stages of their disease, orunder specific circumstances (infections, i.e streptococcal;iatrogenic, i.e. under some atypical neuroleptics, etc).Existence of these three groups may explain (at least, inpart) the diversity in epidemiological data, clinical mani-festations and course, neuropsychological correlates, out-comes of various prognoses and treatments. (Reznik etal.,2004; Bottas et al., 2005, Lee et al., 2009, Kumbhani etal. 2010 )

DIAGNOSTIC CHALLENGES

The differential diagnosis of a patient who presentswith both psychotic and obsessive-compulsive symptomscan include comorbid schizophrenia and obsessive-compulsive disorder, OCD with poor insight, or schizo-phrenia with antipsychotic-induced obsessive-compulsivesymptoms. If the psychotic symptoms are subthreshold orattenuated in form, the individual may have OCD andputative prodromal schizophrenia. No biological markers

exist to differentiate between these possibilities, and thereis debate as to the relationship of schizophrenia and OCD,especially early in the course of evolving symptoms.However, accurate diagnosis is important given that cur-rent treatments for OCD and schizophrenia differ, andfirst-line medications for one may exacerbate the symp-toms of the otherthat is, antipsychotics can exacerbateobsessive-compulsive symptoms, and SRIs may exacer-bate psychosis . Also, the choice of diagnoses made hasprognostic implications. (Rodriguez et al., 2010)

When a patient presents with the hallmarks of schizo-phreniahallucinations, disorganized speech and behav-iour, negative symptoms, and delusions (i.e., erroneousbeliefs that usually involve a misinterpretation of percep-tions or experiences [DSM IV-TR])the diagnosis isusually straightforward. Likewise, when a patient presentswith the hallmarks of OCDobsessions (recurrent orpersistent thoughts, impulses, or images[that are]intrusive and inappropriate and that cause marked anxietyor distress [DSM-IV-TR]) and compulsions (repetitivebehavioursor mental actsthat the person feels drivento perform in response to an obsession[and]are aimedat reducing distress or preventing some dreadedevent[DSM-IV-TR])and has good insight into the irra-tionality of his or her thoughts and the link between his orher thoughts and compulsions, it is clearly OCD.However, in the patient who does not have hallucinationsor disorganized speech but has psychotic beliefs and repet-itive behaviours, it can be a challenge to distinguish thedelusion of schizophrenia from the obsession of OCD ifthe patient has poor or no insight. Another challenge insome cases is to distinguish the repetitive behaviours ofschizophrenia from the compulsions of OCD. Neither ofthe challenge is uncommon. In the absence of biomarkersor behavioural tests that can distinguish these features,careful attention to four aspects of the clinical phenotypecan help in evaluation. (Rodriguez et al. 2010; DSM-IV-TR).

OBSESSIONS VERSUS DELUSIONS

A long-standing challenge facing investigators andclinicians is the difficulty in differentiating an obsessionfrom a delusion when the 2 symptoms appear to be con-nected. Obsessions and delusions are both thought distor-tions. However, the content and character of the distor-tions, as well as their relationship to repetitive behaviours,can differ. In OCD, several common obsessive themeshave been described: contamination, symmetry or exact-ness, forbidden thoughts (aggressive, sexual, religious, andsomatic), and hoarding . These obsessional themes are typ-ically associated with corresponding compulsions: clean-

PRESENT DEFICIENCIES AND FUTURE SKILLS IN CHILDREN WITH ASPERGER SYNDROME


ing, ordering and arranging, checking, and hoarding. Incontrast, the delusions seen in patients with schizophreniainclude persecutory, referential, somatic, erotomanic, andgrandiose themes . This is true even of the overvaluedideas seen in patients who are in a putative prodromalstage . Psychotic beliefs are more often bizarre (clearlyimplausible and not understandable and do not derive fromordinary experiences); however, bizarreness can be dif-ficult to judge, especially across cultures. Althoughsomatic themes overlap between the two disorders,somatic thoughts that are bizarre or represent loss of con-trol over mind or body are more common in schizophre-nia than in OCD with poor insight . Likewise, religiousthemes can occur in both, but in OCD, patients are overlyconcerned with sacrilege, blasphemy, or scrupulosity (i.e.,excessive concern with right and wrong or with morality),whereas in schizophrenia, patients may more commonlyhave grandiose religious delusions (e.g., Im a divinemessenger). Furthermore, loss of control, or agency ofthinking, more commonly occurs in schizophrenia.Patients with OCD often consider their obsessions as prod-ucts of their own thinking, whereas patients with schizo-phrenia often believe that there is some external agency orcause to what they are experiencing and thinking .This dis-tinction, however, becomes blurred when considering indi-viduals with attenuated psychotic symptoms in a putativeprodromal stage of schizophrenia or in patients withschizophrenia whose psychotic symptoms are partiallyremitted or residual. Also, a sense of permeation of egoboundary is more typical of schizophrenia than of OCD,although most patients with schizophrenia also have anintact sense of ego boundary. However, the problem withthese distinctions is that they are less clear in prodromal orevolving stages of illness or with partial remission ofsymptoms during residual phases. For example, youngpeople at heightened risk for schizophrenia have attenuat-ed psychotic symptoms and can retain insight that theirexperiences are likely the product of their own imagina-tion, although doubt may exist as to their source andnature. (Rodriguez et al., 2010; Bottas et al., 2005).

COMPULSION VERSUS REPETITIVEBEHAVIOURS

In adults with OCD, compulsive behaviours are typi-cally performed in response to an obsession and to reducedistress or prevent a dreaded event. In contrast, in schizo-phrenia, repetitive behaviours are often independent ofthought content. The presence of compulsions linked toobsessions may be a useful guide in diagnosing comorbidOCD in patients with schizophrenia. (Rodriguez et al. ,2010; Bottas et al, 2005)

TIME OF ONSET OF SYMPTOMS

Age at onset is similar for both OCD and schizophre-nia, with 50% of OCD cases starting by age 19 and20%40% of first psychotic symptoms in schizophreniastarting by age 20. In both disorders, subsyndromal symp-toms can start in adolescence. However, the time of symp-toms onset in relationship to changes in medication canexclude diagnoses. For example, if the first evidence ofobsessive-compulsive symptoms or an exacerbation ofexisting symptoms occurs after initiating antipsychotictreatment for psychosis, one should consider the possibili-ty that the symptoms are medication induced. Similarly, ifpsychotic symptoms worsen after initiating or titrating anSRI, one should consider the possibility of medication-induced psychosis (Rodriguez et al., 2010).

FAMILY HISTORY

Family history can help inform the differentialdiagnosis. Although both schizophrenia and OCD are her-itable disorders, with higher concordance rates in monozy-gotic twins than in dizygotic twins, they do not appear tocosegregate. Families of patients with schizophrenia aremore likely to have members with schizophrenia spectrumdisorders, such as schizoaffective disorder and schizotypalpersonality disorder . In contrast, families of patients withOCD are more likely to have what are called OCD spec-trum disorders (including tic disorder, Tourettes syn-drome, skin picking) and comorbid mood and anxiety dis-orders . (Rodriguez et al., 2010)

DEVELOPMENTAL PSYCHOSOCIALFUNCTIONING

Both schizophrenia and OCD can lead to significantfunctional impairment in the work, family, and socialdomains. However, in contrast to OCD, social dysfunctionis a core feature of schizophrenia and functional impair-ment is one of the DSM-IV criteria required for diagnosis.In schizophrenia, this social dysfunction is evident early .Itis first expressed subtly during the premorbid period inchildhood as difficulty in establishing relationships andsocial overreactivity (social anxiety, acting out) in boysand underreactivity (withdrawal) in girls . Likewise, ado-lescents at genetic risk for schizophrenia have poor peerengagement and unpopularity with peers .Active socialwithdrawal is a feature of the putative prodromal period inschizophrenia . Lack of interpersonal relatedness (i.e.,diminished capacity for others to feel engaged and relatewell to the individual) may also be characteristic of schiz-ophrenia. In addition to social dysfunction, negative symp-toms (e.g., flat affect, avolition, and alogia) are a key clin-



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ical aspect of schizophrenia and can include social anhedo-nia. In contrast, lack of interpersonal relatedness and socialanhedonia are not characteristic of OCD, and social dys-function is not required for an OCD diagnosis. On theother hand, obsessive-compulsive symptoms can certainlylead to social dysfunction. (Rodriguez et al., 2010)

SUGGESTIONS FOR IDENTIFYING OCS IN THEPRESENCE OF PSYCHOSIS

1. The types of obsessions and compulsions observedin schizophrenia are phenomenologically similar to thosepresent in pure OCD.

2. A repetitious act should be considered a compul-sion only if it occurs in response to an obsession and not ifit occurs in response to psychotic ideation (e.g., repetitivechecking in response to paranoid fears does not constitutea compulsion).

3. A recurrent, intrusive, ego-dystonic thought shouldnot be considered an obsession if it revolves exclusivelyaround current delusional themes (e.g., violent images,which constitute a common type of obsession in OCD,may represent an entirely different phenomenological enti-ty in the context of psychosis). In the acute psychoticphase it may be necessary to exclude questionable obses-sions and reassess for these after the psychotic symptomshave been treated.

4. OCS may be difficult to distinguish in the presenceof thought form disorder; it may therefore be necessary toreassess for OCS once thought form has normalized.

5. Primary obsessional slowness may be mistaken forprodromal schizophrenia or thought disorder; such patientsmay be unable to articulate any obsessions and may exhib-it no compulsions.

6. At times it may not be possible to determine ifapparent OCS in the presence of psychosis represent realOCS; in such cases empiric treatment with a neurolepticand a serotonin reuptake inhibitor (the standard treatmentfor OCD) may be necessary. (Bottas et al, 2005)

NEUROPSYCHOLOGICAL PROFILE OF OBSES-SIVE- COMPULSIVE SCHIZOPHRENIA

OC-schizophrenia patients possess a distinct clinicaland neuropsychological profile that differs from that oftheir non-OC schizophrenic counterparts. This profileincludes a worse clinical course with poor treatmentresponse, lower functioning levels, and greater impairmentof functions primarily subserved by the frontal lobes.(Hwang et al. 2000). Co-occurrence of schizophrenia andOCS reflects the presence of both the structural and func-tional abnormalities associated with schizophrenia and

OCD. Accordingly, it has been suggested that individualswith schizophrenia and OCS/OCD may represent a groupof persons with particularly severe cognitive and function-al deficits. Research supporting this hypothesis includesstudies linking OCS with deficits in several domains ofexecutive function, including abstract reasoning andabstract flexibility (Lysaker et al., 2002, Kumbhani et al,2009, Niendam et al, 2008)

NEUROBIOLOGY

Considerable work has been done to elucidate theneurobiologic basis of both schizophrenia and OCD.Serotonin and dopamine have most consistently emergedas the principal neurotransmitters of interest in both disor-ders. In schizophrenia, the dopamine hypothesis has longbeen regarded as the fundamental neurochemical premise;this is most strongly supported by successful treatment ofthe disorder with dopamine receptor antagonists.However, the superior efficacy of the serotonindopaminereceptor antagonists in the treatment of schizophreniaadditionally supports the importance of the serotonergicsystem in the pathophysiology of this disorder and mayreflect the modulation of dopaminergic systems by sero-tonin. Conversely, in OCD a somewhat opposing picturehas emerged with respect to neurotransmitter involvement.The serotonin hypothesis of OCD is supported by success-ful treatment of the disorder with serotonin reuptakeinhibitors. Pharmacologic challenge studies with serotoninagonists and cerebrospinal fluid neurotransmitter metabo-lite studies have provided further evidence for the involve-ment of the serotonergic system in OCD. However, not allstudies support a singular role for serotonin in OCD.Typically only 40%60% of patients with OCD exhibitresponse to monotherapy with selective serotonin reuptakeinhibitors, and the magnitude of response is often modest.This observation suggests the involvement of other neuro-transmitter systems in the pathophysiology of OCD, andevidence supporting the role of the dopaminergic systemin this disorder has led to a proposed dopamineserotoninhypothesis of OCD. Several lines of evidence implicatethe dopaminergic system in the pathophysiology of OCD,including the role of dopamine in stereotypic behaviours inanimal models, the etiologic role of dopamine inTourettes disorder (which is frequently comorbid withand shares neuroanatomic substrates with OCD), preclini-cal evidence of dopamines reciprocal modulatory effectson the serotonin system and successful treatment of refrac-tory OCD with dopamine receptor antagonists and sero-tonindopamine receptor antagonists. The latter observa-tion (of the therapeutic utility of antipsychotic medicationsin OCD) is difficult to interpret, given numerous reports of

PRESENT DEFICIENCIES AND FUTURE SKILLS IN CHILDREN WITH ASPERGER SYNDROME


the emergence of de novo OCD or exacerbation of pre-existing OCD in patients with schizophrenia who havebeen treated with atypical antipsychotics. Such paradoxi-cal findings are a testimony to the extreme complexity ofthe neurotransmitter systems involved in each disorder.(Bottas et al., 2005; Poyurovsky et al 2007, Hwang et al.2000)

NEUROANATOMY AND NEUROCIRCUITRY

Several investigators have hypothesized that similari-ties in the neurocircuitry and specific anatomic structuresimplicated in each disorder may account for symptom co-expression. The functional circuitry involved in the patho-physiology of OCD is generally believed to involve a cor-tico-striatal-thalamic-cortical circuit. Specific structuresinvolved in this pathway include the basal ganglia,orbitofrontal cortex and anterior cingulate cortex. In schiz-ophrenia, the dorsolateral prefrontal cortex circuit containsanatomic substrates similar to those of the OCDorbitofrontal circuit. Thus, the specific neuroanatomicsites identified by structural and functional neuroimagingstudies performed in each of these disorders independent-ly show considerable overlap in implicated structures,including the basal ganglia, thalamus, anterior cingulum,orbitofrontal cortex and regions of the temporal cortex,although some of these findings are controversial. (Bottaset al., 2005; Poyurovsky et al 2007)

NEUROIMAGING STUDIES

Neuroimaging studies suggest that there may be aspecific pattern of neuroanatomic dysfunction in thecomorbid subgroup. Aoyama et al performed MRI in sub-jects with juvenile-onset schizophrenia and OCS andfound significantly smaller left hippocampi in this groupthan in subjects who had schizophrenia without OCS andin control groups. These researchers also found an inversecorrelation between illness duration and frontal lobe sizein the group with both schizophrenia and OCS, but not inthe group with schizophrenia only. In another MRI studyof patients with juvenile-onset schizophrenia, investigatorsdemonstrated significant enlargement of the anterior hornof the lateral ventricle and the third ventricle in patientswith OCS relative to those without OCS. In a study offunctional MRI performed on patients with schizophreniaand various degrees of OCS, one subgroup exhibited anegative correlation between activation of the left dorso-lateral prefrontal cortex and OCS severity. Taken together,these findings suggest specific neuroanatomic abnormali-ties in the overlap group that differ from what is observedin each disorder individually. (Bottas et al., 2005)

PRINCIPLES OF TREATMENT

A few studies have addressed how to treat patientswith both schizophrenia and OCD . Based on these stud-ies, OCD treatment guidelines suggest that these patientsshould first be stabilized on a second-generation antipsy-chotic and the obsessive-compulsive symptoms subse-quently treated by the addition of an SRI. Whether thesepatients require SRIs at the high doses needed in patientswith OCD without a comorbid psychotic disorder isunclear: obsessive-compulsive symptoms in the context ofpsychotic disorder have been found to respond to lowerdoses of fluvoxamine (100200 mg/day) than typicallyused in treatment of OCD (250300 mg/day). Poyurovskyand colleagues proposed that those who do not respond tothe steps above be switched to another SRI orclomipramine, to another second-generation antipsychotic,or to a first-generation antipsychotic with an SRI orclomipramine. If these strategies are ineffective, they pro-pose clozapine at a low dosage (75300 mg/day), SRI aug-mentation of clozapine, and finally ECT . Combiningantipsychotics and SRIs (e.g., fluvoxamine and clozapine;clomipramine and clozapine; paroxetine and risperidone ora phenothiazine) requires careful monitoring for drug-druginteractions and for possible exacerbation of obsessionalor psychotic symptoms . In patients with co-occurringschizophrenia and OCD or obsessive-compulsive symp-toms, if antipsychotic medication induces obsessive-com-pulsive symptoms, there are several options: waiting forspontaneous resolution (46 weeks), gradually reducingthe dosage of antipsychotic, switching to another antipsy-chotic, adding an SRI to target the obsessive-compulsivesymptoms (e.g., fluvoxamine, clomipramine, sertraline),or attempting a trial of exposure and response prevention .The evidence base for these approaches is limited. Somepatients with both schizophrenia and OCD, remain symp-tomatic despite the treatment recommendations listedabove. Recent data have implicated glutamatergic abnor-malities in the pathophysiology of schizophrenia, OCD,and depression . Lamotrigine is an anticonvulsant typical-ly used for seizure disorders and maintenance treatment inbipolar disorder. In addition to its varied mechanisms ofaction, lamotrigine inhibits glutamate release. In schizo-phrenia, there is preliminary evidence that lamotrigine (atdosages of 200 mg/day and higher) might be effective forpsychotic symptoms when added to clozapine but notwhen added to antipsychotics other than clozapine. InOCD, an open-label study found that one of eight patientsresponded to lamotrigine augmentation of an SSRI(although the lamotrigine dosage was only 100 mg/day),and there has been a case report of marked improvementwith lamotrigine augmentation (150 mg/day) of clomip-

ramine. Although no randomized clinical trials have yetbeen conducted to evaluate the efficacy of lamotrigine forpatients with comorbid OCD and schizophrenia, these pre-liminary data suggest that glutamate modulators may be anarea of interest for treatment-resistant patients with bothpsychotic and obsessive-compulsive symptoms. There areas yet no consensus guidelines for the treatment of theputative schizophrenia prodrome. Olanzapine has unclearefficacy and problematic side effects and one study report-ed efficacy with risperidone when administered in combi-nation with CBT . It remains unknown whether treatingobsessive-compulsive symptoms in a putative schizophre-nia prodrome has an effect on the natural course of eitherof these illnesses (Rodriguez et al, 2010).

CONCLUSIONS

Despite the growing evidence supporting the exis-tence of an epidemiologic and biologic relation betweenOCD and schizophrenia, the association remains poorlyunderstood. Although the distinction between obsessionsand delusions is often unclear, clinical evidence suggeststhat OCS in schizophrenia represents more than just anexpression of enduring psychosis. The epidemiologic datasuggest a unique relation between these 2 disorders, giventhe marked degree of comorbidity that has been observed.Furthermore, the neurobiologic data on each disorder sug-gest the involvement of common brain regions and neuro-transmitter systems. In patients with both schizophreniaand OCD more severe impairment was generally revealedthan among patients who have schizophrenia and not OCD(and patients who have OCD and not schizophrenia), whichsuggests a specific and active interaction between these 2disease processes. Further research focusing specifically onthis overlap group is essential and should clarify the natureof this putative entity in the years to come.

REFERENCES

1. Alexandra Bottas, MD; Robert G. Cooke, MD;Margaret A. Richter, MD (2005) - Comorbidity and patho-physiology of obsessivecompulsive disorder in schizo-phrenia: Is there evidence for a schizo-obsessive subtypeof schizophrenia? J Psychiatry Neurosci; 30-3

2. American Psychiatric Association: Diagnostic andStatistical Manual of Mental Disorders, 4th ed, TextRevision (DSM-IV-TR) (1994) - Washington, DC,American Psychiatric Association

3. Carolyn I. Rodriguez, M.D., Ph.D.; CherylCorcoran, M.D.; Helen Blair Simpson, M.D., Ph.D. (2010)- Diagnosis and Treatment of a Patient With BothPsychotic and Obsessive-Compulsive Symptoms; Am JPsychiatry; 167:754761

4. Glcan GLE, Elif GNE, nar YENLMEZ(2008) - Comparison of Patients with Schizophrenia,Obsessive- Compulsive Disorder, and Schizophrenia withAccompanying Obsessive-Compulsive Symptoms; TurkishJournal of Psychiatry ;19-3

5. Michael Poyurovsky, M.D.; Sarit Faragian, M.A.;Artashes Pashinian, M.D.; Aya Levi, M.A.; AlexanderViosburd, M.D.; Raphael Stryjer, M.D.; Ronit Weizman,M.D.; Camil Fuchs, Ph.D.; Abraham Weizman, M.D.(2007) - Neurological Sof Signs in Schizophrenia PatientsWith Obsessive-Compulsive Disorder; The Journal ofNeuropsychiatry and Clinical Neurosciences; 19:145150

6. Michael Y. Hwang, M.D.; Joel E. Morgan, Ph.D.;Miklos F. Losconzcy, M.D., Ph.D (2000) - Clinical andNeuropsychological Profiles of Obsessive-CompulsiveSchizophrenia: A Pilot Study; The Journal ofNeuropsychiatry and Clinical Neurosciences; 12:9194

7. Myung-Ji Lee; Yong-Bum Shinl ; Young-KyungSunwoo; Seung-Ho Jung; Won-Hyoung Kim; Min-HeeKang; Jeong-Seop Lee; Jae-Nam Bae; Chul-Eung Kim(2009) - Comparative Analysis of Cognitive Function inSchizophrenia with and without Obsessive CompulsiveDisorder; Official Journal of Korean NeuropsychiatricAssociation; 6:286-293

8. Paul H. Lysaker, Ph.D.; Gary J. Bryson, Psy.D.;Kriscinda A. Marks, M.S.; Tamasine C. Greig, Ph.D.;Morris D. Bell, Ph.D.(2002) - Association of Obsessionsand Compulsions in Schizophrenia With Neurocognitionand Negative Symptoms ; The Journal of Neuropsychiatryand Clinical Neurosciences; 14:449453

9. Paul H. Lysaker, Ph.D., Kriscinda A. Whitney,Ph.D., Louanne W. Davis, Psy.D (2009) - Associations ofExecutive Function With Concurrent and ProspectiveReports of Obsessive-Compulsive Symptoms inSchizophrenia; The Journal of Neuropsychiatry andClinical Neurosciences; 21:3842

10. Reznik I, Yavin I, Stryjer R, et al (2004):Clozapine in the treatment of obsessive-compulsive symp-toms in schizophrenia patients: a case study ;Pharmacopsychiatry,; 37:52-56

11. Sheba R. Kumbhani, Ph.D. Robert M. Roth, Ph.D.Carrie L. Kruck, M.Psych. Laura A. Flashman, Ph.D.Thomas W. McAllister, M.D (2010) - NonclinicalObsessive-Compulsive Symptoms and Executive Functionsin Schizophrenia; The Journal of Neuropsychiatry andClinical Neurosciences; 22:304 312

12.Tara A. Niendam, Ph.D. Jodi Berzaka, Tyrone D.Cannon, Ph.D. and Carrie E. Bearden, Ph.D. (2009) -Obsessive Compulsive Symptoms in the PsychosisProdrome: Correlates of Clinical and Functional Outcome;Schizophr Res.; 108(1-3): 170175

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Schizophrenia and Obsessive Compulsive Disorder

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