Epilepsy & Behavior 14 (2009) 634–639

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Epilepsy & Behavior

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A comparative study of obsessive–compulsive disorder and other psychiatriccomorbidities in patients with temporal lobe epilepsy and idiopathicgeneralized epilepsy

Banu Aslantas� Ertekin a,*, Is�ın Baral Kulaksızoglu a, Erhan Ertekin a, Candan Gürses b, Nerses Bebek b,Ays�en Gökyigit b, Betül Baykan b

a Department of Psychiatry, Istanbul Medical Faculty, Istanbul University, Millet Cad. Capa, Istanbul, Turkeyb Department of Neurology, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey

a r t i c l e i n f o

Article history:Received 1 December 2008Revised 18 January 2009Accepted 22 January 2009Available online 14 February 2009

Keywords:EpilepsyPsychiatric comorbidityObsessive–compulsive disorderLateralizationTemporal lobe epilepsy

1525-5050/$ - see front matter � 2009 Elsevier Inc. Adoi:10.1016/j.yebeh.2009.01.016

* Corresponding author.E-mail address: banu_aslantas@yahoo.com (B.A. E

a b s t r a c t

Our aim was to assess the associations of temporal lobe epilepsy (TLE) and idiopathic generalized epi-lepsy (IGE) with comorbid psychiatric conditions, especially obsessive–compulsive disorder (OCD), in acomparative design. We evaluated 29 patients with TLE, 27 patients with IGE, and 30 healthy controls.The Structured Clinical Interview for DSM-IV (SCID), Yale–Brown Obsessive Compulsive Scale (Y-BOCS)Symptom Checklist, and Beck Depression Inventory (BDI) were administered. Among patients withTLE, 75.9%, and among patients with IGE, 48.1% had at least one Axis I psychiatric disorder. Clinicallymeaningful obsessive–compulsive symptoms (CM-OCS) were noted in 10 patients with TLE and in 3patients with IGE, and this difference was statistically significant (P < 0.05). CM-OCS were present in 9of 18 patients with left-sided TLE, but in only 1 of 11 patients with right-sided TLE. Higher comorbidityin TLE suggests that involvement of the temporal lobe may play a role in the development of specific psy-chopathological syndromes.

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1. Introduction

Epilepsy is one of the most common chronic neurological disor-ders, with a prevalence of 0.4–1% in different studies [1–3]. Be-cause it may have consequences in emotional, behavioral, social,and cognitive domains, psychiatric comorbidity in epilepsy has be-come a major area of interest. There is considerable evidence in theliterature suggesting that the risk for psychiatric comorbidity is in-creased in patients with epilepsy. Psychiatric comorbidity occurs in20–40% of patients with epilepsy, and it is even more frequent inpatients with refractory seizures [4]. A study including 60 patientswith refractory epilepsy reported that approximately 70% had acomorbid psychiatric disorder [5]. In a recent review, it was re-ported that the prevalence rates of Axis I psychiatric disorders inpatients with epilepsy vary between 19% and 80% [6]. Comparedwith adults without epilepsy, adults with partial/complex partialepilepsy had higher rates of clinically significant mental healthsymptoms as measured with the Symptom Checklist-90—Revised(SCL-90-R). Eighty-eight percent of adults with partial epilepsyhad one or more elevated index or symptom scale scores [7].

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rtekin).

Mood disorders are considered the most frequent psychiatriccomorbidity in patients with epilepsy [8]. Although most of theattention has been focused on depression, anxiety symptoms arecommon [9], and anxiety disorders are prevalent comorbiditiesamong people with epilepsy [10]. A population-based study con-ducted in Canada revealed that lifetime prevalences of mood disor-ders and anxiety disorders were quite similar in people withepilepsy (24.4% and 22.8%, respectively) [11]. Swinkels and col-leagues used the Composite International Diagnostic Interview(CIDI) to assess psychiatric comorbidity in patients with differenttypes of epilepsy. They evaluated 209 patients, and the 1-yearprevalence of anxiety disorders was 24.9%, whereas the prevalenceof mood disorders was 18.7% [12].

It has been suggested that the involvement of different brainstructures in different types of epilepsy may play a role in thedevelopment of specific psychopathological syndromes [13]. Be-cause the limbic system includes the medial parts of the temporallobes, more psychiatric disturbances may be expected in patientswith an epileptic focus in temporal regions of the brain [6].Whether patients with temporal lobe epilepsy (TLE) are at in-creased risk of developing psychiatric disorders as compared withpatients with other types of epilepsy remains an open question.Perini et al. [14] reported significantly higher psychiatric comor-bidity in patients with TLE (80%) than in patients with juvenile

B.A. Ertekin et al. / Epilepsy & Behavior 14 (2009) 634–639 635

myoclonic epilepsy (22%) or diabetes (10%), which was included inthe study as a chronic medical condition for control purposes.However, there are also studies in the literature that have foundno evidence to support a specific relationship between the typeor focus of epilepsy and psychopathology [15].

The limbic system appears to be involved in the pathophysiol-ogy of obsessive–compulsive disorder (OCD). Therefore, OCD isone of the psychiatric disorders that can be expected to be foundmore commonly in patients with TLE. There are case studies andclinical observations in the literature reporting an association be-tween TLE and OCD [16–19]. One study indicated a 22% prevalenceof obsessive–compulsive symptoms (OCS) in a group of 30 patientswith drug-resistant epilepsy [20]. In another study using the SCIDto diagnose OCD, Monaco et al. found that 14.5% of patients withTLE have OCD [13].

Whether the lateralization of temporal seizures has an effect onOCD comorbidity is a controversial issue. Schmitz and colleagues[21] did not find evidence to support the notion that lateralizedepileptogenic lesions are associated with different levels of depres-sion, obsessionality, or personality traits. On the other hand, Isaacset al. [20] found that patients with right-sided seizures scoredhigher on the Obsessive Compulsive Inventory (OCI) than thosewith left-sided seizures. Although this difference was not statisti-cally significant, the authors stated that right hemispheric involve-ment in patients with TLE may increase their likelihood ofexperiencing OCS.

The aim of this study was to assess the associations of TLEcaused by unilateral mesial temporal sclerosis (MTS) and idio-pathic generalized epilepsy (IGE) with psychiatric comorbiditiesand especially with OCD in a comparative design. We also aimedto evaluate the effect of lateralization and the differences in obses-sive and compulsive domains between these groups.

2. Methods

We evaluated 29 patients with TLE (mean age: 32.9 ± 11.3,range: 18–68 years) who came to our clinic for their routine visitswithin the study period and 27 patients with idiopathic general-ized epilepsy (IGE) (mean age: 32.9 ± 10.4, range: 19–54 years)who were matched with the TLE group with respect to age, gender,marital status, education, handedness, and duration of epilepsy.Epilepsy syndromes were diagnosed according to InternationalLeague Against Epilepsy (ILAE) criteria [22]. The control group con-sisted of 30 volunteers without epilepsy and without a history ofany chronic disease, matched with the epilepsy groups on theaforementioned demographic characteristics.

All patients were assessed by at least two experienced epilep-tologists from the Epilepsy Unit, Department of Neurology, Istan-bul Medical Faculty, Istanbul University, which is a well-established tertiary referral center for patients with epilepsy inTurkey. Patients’ histories of delivery and developmental statuswere evaluated, and histories of familial febrile seizures and epi-lepsy were elicited. Detailed epilepsy history assessment and neu-rological examinations were conducted.

All patients had had at least one diagnostic EEG. Our routineEEG protocol for IGE established after 1990 includes hyperventila-tion and intermittent photic stimulation as described in detail pre-viously [23]. All patients with TLE had undergone at least onenoninvasive video/EEG monitoring study that revealed complexpartial seizures of unilateral temporal lobe onset and a diagnosticMRI scan as described below. The consecutive patients who ful-filled these inclusion criteria and were able to read and write wereincluded in the study after giving their informed consent. The pa-tients in the sample were not preselected or excluded for any psy-chiatric history, but those patients already operated for MTS were

not included to exclude the effect of the operation on the naturalcourse. No specific treatment regimen, laboratory investigations,or EEG controls were planned for them, and they were managedaccording to the clinical needs, as were all other patients withIGE and TLE in the epilepsy unit.

Treatment resistance was defined as using more than one AEDand having two or more seizures per month. Treatment resistancedata were collected from medical records and self-reports of theparticipants with epilepsy.

MRI studies were performed with a 1.5-T scanner (MagnetomSiemens Symphony, Erlangen, Germany) according to a standardprotocol. MRI findings of atrophy and high signal changes in thehippocampus on T2-weighted and FLAIR (fluid-attenuated inver-sion recovery) sequences and loss of visualization of the internalstructures of the hippocampus were the diagnostic criteria forMTS [24–26].

All study subjects were evaluated in the Department of Psychi-atry, Istanbul Medical Faculty, by one of the authors (B.A.E., E.E.),trained 4-year psychiatry residents under the supervision of anexperienced psychiatrist (I.B.K.). At the first stage, all subjects wereevaluated with the Structured Clinical Interview for DSM-IV Pa-tient Version (SCID-I/P) for psychiatric diagnoses, the Yale BrownObsessive Compulsive (Y-BOCS) Symptom Checklist, and the BeckDepression Inventory (BDI).

Subsyndromal OCD was considered when subjects met all crite-ria for OCD except for recognition that symptoms did not cause sig-nificant distress, last longer than 1 h, or interfere significantly withdaily life. When patients’ complaints were nothing more than justthe obsessions or compulsions, they were considered only to haveOCS [27] and not classified as having a clinically meaningful condi-tion or disease. In this study, because we were evaluating psychi-atric comorbidity in patients with epilepsy, we considered onlysubsyndromal OCD and OCD as clinically meaningful OCS (CM-OCS). For participants who had subsyndromal OCD and OCD, wealso measured the severity of their symptoms with the Y-BOCSSeverity Scale.

3. Measures

The Structured Clinical Interview for DSM-IV Axis I Disorders(SCID-I) is a semistructured interview for diagnosing the majorDSM-IV Axis I disorders. SCID-I is designed to yield a reliable andvalid DSM-IV Axis I diagnosis and is considered the standard re-search tool for this purpose. The SCID-I/P is ordinarily administeredin a single setting and takes 45–90 minutes [28].

OCD symptoms were assessed with the clinician-rated Y-BOCSSymptom Checklist, which includes more than 50 types of obses-sions and compulsions divided into 13 major categories and 2 cat-egories of miscellaneous obsessions and compulsions. Thedimensional structure of the Y-BOCS Symptom Checklist has beenreasonably replicated, and the symptom dimensions are relativelyindependent of overall symptom severity [29].

Y-BOCS is designed to rate the severity of symptoms in patientswith OCD. The Y-BOCS provides five rating dimensions for obses-sions and compulsions: time spent or occupied; interference withfunctioning or relationships; degree of distress; resistance; andcontrol (i.e., success in resistance). The 10 Y-BOCS items are eachscored on a 4-point scale from 0 = ‘‘no symptoms” to 4 = ‘‘extremesymptoms.” The sum of the first five items is a severity index forobsessions, and the sum of the last five is an index for compulsions.The following total scores are considered as a severity index forOCD symptoms: 0–7 subclinical, 8–15 mild, 16–23 moderate, 24–31 severe, 32–40 extreme [30,31].

The BDI is a 21-item self-report instrument intended to assessthe existence and severity of symptoms of depression. Each of

636 B.A. Ertekin et al. / Epilepsy & Behavior 14 (2009) 634–639

the 21 items corresponds to a symptom of depression and is ratedon a 4-point scale from 0 to 3. A total score is determined by aggre-gating the item responses and may range from 0 to 63 (normal tosevere). BDI scores above the 14 cutoff may indicate the presenceof depression [32].

We investigated the psychiatric comorbidity, especially theoccurrence of subsyndromal OCD as well as full OCD, in patientswith TLE, those with IGE, and controls and compared the domainswith each other. Special emphasis was placed on characterizing thedifferences in self-reported OCS types between the subgroups andin patients with right and left hemisphere TLE.

We used Fisher’s exact tests and v2 analyses for categorical dataand one-way ANOVA for comparing the three groups. Statisticalanalyses were performed using SPSS Version 15 for Windows.

4. Results

We enrolled a total of 86 subjects with a mean age of31.7 ± 10 years. The three groups—TLE, IGE, and control—did notstatistically differ significantly on age (v2(2) = 2.35, P = 0.309), gen-der (v2(2) = 0.485, P = 0.785), educational level (v2(2) = 2.49,P = 0.257), marital status (v2(2) = 0.715, P = 0.700), and handed-ness (Fisher’s exact test: df = 1, P = 1.000). Duration of epilepsywas similar in the two epilepsy groups (Mann–Whitney U test:Z = �1.31, P = 0.192). In the TLE group, 11 patients were using anti-epileptic drug (AED) monotherapy and 18 patients were under apolytherapy regimen. The most commonly used drugs were car-bamazepine (62.0%), barbexaclone (24.1%), and topiramate(20.6%). In the IGE group, 16 patients were using monotherapyand 9 patients were using polytherapy. There were also two pa-tients whose drugs were discontinued because of their clinicalwell-being. The most commonly used drugs in this group were val-proate (66.7%) and barbexaclone (18.5%). In the TLE group 55.1% ofthe patients were treatment resistant, and this proportion was only14.8% in the IGE group. Table 1 summarizes the demographic andclinical data.

Axis I psychiatric comorbidity rates were significantly higher inpatients with TLE; 22 patients with TLE (75.9%), 13 patients withIGE (48.1%), and 5 healthy controls (16.7%) met criteria for at leastone Axis I psychiatric disorder (v2(2) = 20.812, P = 0.0001) (Table2).

According to the SCID, three patients (10.3%) in the TLE group,only one in the IGE group (3.7%), and none in the control groupmet criteria for a diagnosis of OCD. In general, CM-OCS were ob-served in 10 patients with TLE (3 with OCD and 7 with subsyndro-mal symptoms), and 6 of these patients also had a depressivedisorder. On the other hand, only 3 patients with IGE had CM-OCS (1 with OCD and 2 with subsyndromal symptoms), and thiswas significantly lower than in the TLE group (v2(1) = 4.285,P = 0.038). Interestingly, the prevalence of CM-OCS significantlydiffered with respect to lateralization of the epileptic focus in pa-

Table 1Demographic and clinical features of the three study groups.

TLE group (n = 29) IGE grou

Age (years), mean ± SD 32.9 ± 11.3 32.9 ± 1Gender (female/male) 14/15 15/12Marital status (single/married) 12/17 14/13Education (years) 9.0 10.33Age at onset of epilepsy 16.2 13.9Duration of epilepsy (years) 16.9 19.6AED therapy (mono/poly/none) 11/18/0 16/9/2Carbamazepine (mono/poly/total) 7/11/18 0/1/1Valproate (mono/poly/total) 0/1/1 13/5/18All other AEDs (mono/poly/total) 4/17/21 3/8/11Treatment resistance (+/-) 16/13 4/23

tients with TLE: CM-OCS were present in 9 of 18 patients with lefthemisphere MTS (2 with OCD, 7 with subsyndromal OCD), but inonly 1 of 11 patients with right hemisphere MTS (1 with OCD)(Fisher’s exact test: P = 0.044).

For the two epilepsy groups combined, the most common typesof obsessions were symmetry/exactness (n = 8), contamination(n = 8), aggressiveness (n = 6), and miscellaneous (n = 6) (fear ofnot saying just the right thing in 4 patients, fear of saying certainthings in 2 patients, fear of losing things in 2 patients, superstitiousfears in 1 patient, and need to know or remember in 1 patient)obsessions. The most common compulsions were ordering(n = 8), washing (n = 6), and checking (n = 5). The Y-BOCS SymptomChecklist revealed that the patients with TLE had significantlyhigher contamination obsessions (Fisher’s exact test: P = 0.005)and washing compulsions (Fisher’s exact test: P = 0.024) than thepatients with IGE. Although below the level of statistical signifi-cance, symmetry/exactness obsessions and ordering compulsionsexhibited a trend toward being more common in patients withTLE than in patients with IGE (Fisher’s exact test: P = 0.052 forboth) (Table 3).

The mean severity of OCD was Y-BOCS = 12.90 in the TLE groupand Y-BOCS = 11 in the IGE group. These scores were consideredwithin the range of medium severity, and the difference betweenthem was not statistically significant.

There were no significant differences between the groups withrespect to BDI scores, although depressive disorders (MajorDepressive Disorder, Dysthymic Disorder, and Depressive DisorderNot Otherwise Specified) were slightly more frequent in patientswith TLE than in patients with IGE. In both epilepsy groups, depres-sive disorders were frequently seen with obsessionality: 6 of 10patients with CM-OCS in the TLE group and 2 of 3 patients withCM-OCS in the IGE group also had a depressive disorder.

5. Discussion

In this study we found that psychiatric comorbidity rates weresignificantly higher in patients with TLE than in patients with IGEand control subjects: 10.3% of patients with TLE had OCD and 24.1%had subsyndromal OCD in TLE group. These rates were also numer-ically, but not statistically, higher than those for the matched IGEgroup (3.7% and 7.4%, respectively). In the TLE group, left-sided le-sions were more likely to be associated with OCD. Depression wasthe most common comorbidity with OCD and the co-occurrence ofthese disorders was also noticeable.

High psychiatric comorbidity in chronic medical conditions hasbeen reported in many studies [33]. Living with a chronic disease,restrictions in daily routines, or low quality of life may facilitatethe development of comorbid psychiatric conditions, especiallydepression. Some authors have suggested that psychopathologyis generally associated with epilepsy and differences may be dueto disease severity and psychosocial aspects, with no specific rela-

p (n = 27) Control group (n = 30) Significance

0.4 29.6 ± 8.3 v2(2) = 2.35, P = 0.30917/13 v2(2) = 0.485, P = 0.78515/15 v2(2) = 0.715, P = 0.70010.33 v2(2) = 2.49, P = 0.257— v2(1) = 0.313, P = 0.576— Z = –1.31, P = 0.192————— v2 = 6.951, P = 0.008

Table 2Comorbid psychiatric diagnoses as measured with the SCID-I/P.

Psychiatric diagnosis TLE group (n = 29) IGE group (n = 27) Control group (n = 30)

OCD 3 (10.3%) 1 (3.7%) 0Subsyndromal OCD 7 (24.1%) 2 (7.4%) 0Major Depressive Disorder 5 (17.2%) 6 (22.2%) 1 (3.3%)Depressive Disorder NOSa 2 (6.8%) 1 (3.7%) 2 (6.6%)Dysthymic Disorder 2 (6.8%) 0 1 (3.3%)Social Anxiety Disorder 2 (6.8%) 1 (3.7%) 0Posttraumatic Stress Disorder 0 1 (3.7%) 0Generalized Anxiety Disorder 0 2 (7.4%) 0Specific Phobia 4 (13.7%) 1 (3.7%) 0Anxiety Disorder NOS 3 (10.3%) 0 1 (3.3%)Adjustment Disorder 3 (10.3%) 1 (3.7%) 0Psychotic Disorder NOS 1 (3.4%) 0 0

a NOS, not otherwise specified.

Table 3Obsessive–compulsive symptom types found in patients with epilepsy.

TLE with OCDa (n = 10) IGE with OCDa (n = 3) P

ObsessionsAggressive 4 2 nsContamination 8 0 0.005Sexual 1 1 nsHoarding 1 0 nsReligious 0 1 nsSymmetry/exactness 7 1 0.052Somatic 0 1 nsMiscellaneous 5 1 ns

CompulsionsWashing 6 0 0.024Checking 4 1 nsRepeating 1 0 nsCounting 2 1 nsOrdering 7 1 0.052Hoarding 1 0 nsMiscellaneous 0 1 ns

a Includes both patients with subsyndromal OCD and those with full OCD.

B.A. Ertekin et al. / Epilepsy & Behavior 14 (2009) 634–639 637

tionship to a generalized or localized syndrome [34]. On the otherhand, besides being a chronic disease with accompanying psycho-social difficulties, epilepsy as a neurological disorder may bringadditional risk for the development of psychiatric disorders.

It has been suggested that the etiology of psychiatric comorbid-ity in patients with epilepsy is multifactorial and probably involvesboth neurobiological and psychosocial factors [35]. In their reviewarticle, Swinkels and colleagues concluded that the chronicity ofepilepsy was important in the predisposition to psychiatric comor-bidity, but that brain dysfunction could bring an additional risk,probably related to involvement of the limbic system [6]. The lackof a significant association with age at onset of epilepsy and dura-tion of epilepsy suggests that the biological theories of anatomicalconnections may be more important than the chronicity of epi-lepsy in explaining our findings.

In our study, OCD and multiple psychiatric comorbidities weremore common in patients with TLE than in patients with IGE. Thisfinding is consistent with the results of some studies [14]. Comor-bidity between OCD and epilepsy, especially TLE, has been reportedin several case studies and case series [16–18,20,36–38]. The high-er rates of comorbid depression and anxiety, especially OCD, in pa-tients with TLE suggest that involvement of the temporal lobe mayplay a role in the development of specific psychopathologicalsyndromes.

Monaco et al. [13] found that 14.5% of 62 patients with TLE hada diagnosis of OCD, whereas there was no comorbid OCD among 20patients with IGE. In that study, patients with TLE and OCD differedsignificantly with respect to comorbid depression when compared

with patients with TLE without OCD. In our study, we found that10.3% of patients with TLE had OCD and most of the patients withTLE with OCD also had a depressive disorder. These high preva-lences of OCD and OCD–depression comorbidity are in line withthe results of the Monaco et al. study and may indicate a specifictendency to develop OCD and depression together in patients withTLE. Isaacs et al. [20], using the Obsessive Compulsive Inventory(OCI) [39], reported a 22% prevalence of OCS in patients withdrug-resistant TLE, but they did not use a structured interview todiagnose OCD. By contrast, we and Monaco et al. used the SCID-IP and Y-BOCS to evaluate OCD prevalence.

In addition to clinical obsessions and compulsions, obsessivepersonality traits are also frequent and a cause of low quality of lifein patients with epilepsy [40,41]. Waxman and Geschwind coinedthe term interictal behavior syndrome to describe a distinct subsetof disrupted behaviors believed to be associated with TLE, includ-ing circumstantiality, altered religious and sexual concerns, andhypergraphia [42]. Later, Bear and Fedio extended this syndrometo include obsessionality [43]. Monaco et al. [13] also evaluatedobssesionality as a trait in patients with TLE and IGE. They foundthat the obsessiveness scores were significantly higher in the TLEgroup than in the IGE group, and we recently showed that preop-erative obsessive traits should be taken into consideration in coun-seling for and clinical follow-up of epilepsy surgery in patientswith MTS, because they could manifest as full-blown OCD aftersurgery in some patients [44].

We excluded OCS that occur rarely, last for a very short time,and cause no significant distress at all. On the other hand, thereare patients who suffer a great deal of distress from OCS despitefailing to meet full DSM-IV criteria for OCD. We grouped these pa-tients with subsyndromal OCD together with patients with fullOCD under the heading ‘‘CM-OCS” to gain a broader perspectiveand to avoid underestimating the importance of OCS to patientswith TLE. It has been reported that treatment of OCS could signif-icantly improve the quality of life of patients with TLE [20].

Isaacs et al. found that patients with right-sided seizures scoredan average of 10 points higher on the OCI than those with left-sided seizures, but this difference did not reach the level of statis-tical significance. Meanwhile, there were no differences in OCDwith respect to laterality of the EEG focus in the Monaco et al.study. Although far from being conclusive because of the smallsample size, the findings of our study suggest that left-sided le-sions are more likely to be associated with OCD and OCD–depres-sion comorbidity.

Prefrontal–subcortical circuits are involved in the pathophysiol-ogy of OCD [45]. OCD in patients with focal brain lesions may bedue to structural damage to specific frontal–limbic–subcortical cir-cuits [46]. Functional neuroimaging studies indicate that OCDsymptoms are associated with increased activity in the orbitofron-

638 B.A. Ertekin et al. / Epilepsy & Behavior 14 (2009) 634–639

tal cortex, caudate nucleus, thalamus, and anterior cingulate gyrus[47]. It has been reported that neural dysfunctions in the frontal–subcortical circuits are probably more pronounced in the righthemisphere [48]. However, in a quantitative EEG study, patientswith OCD showed frontotemporal dysfunction, predominantly inthe left hemisphere [49]. The co-occurrence of OCD and left-sidedTLE or other brain lesions has also been described [18,50]. Whenthese results are considered together, we can only conclude thatthe relationship between lateralization of TLE and OCD comorbid-ity is complex, and future studies using larger samples are neededto explain this topic convincingly.

In our study, patients with TLE had significantly higher contam-ination obsessions and washing compulsions than patients withIGE. In addition, symmetry/exactness obsessions and orderingcompulsions revealed a trend very close to statistical significance.Isaacs et al. reported that OCS in patients with TLE was orientedpredominantly around checking, ordering, hoarding, washing, neu-tralizing and doubting. These results can be considered concordant,but there is a clear need for studies of larger sample populations tocharacterize the types of OCS in patients with TLE.

On the other hand, obsessions and compulsions seen in patientswith TLE and IGE may differ from the OCS of patients without epi-lepsy who have OCD. In the present study there were five patientswho had miscellaneous obsessions. Some other obsessions may nothave been detected because these scales were developed for pa-tients with OCD and not for patients with epilepsy. For example,in a recent study by Mula et al. [51], patients with TLE reportedmore obsessions relating to existential attitudes toward religion.Given the frequent occurrence of other OCS like compulsive writ-ing and preoccupation with religious themes or objects in patientswith epilepsy, the development of a new scale that measures thesedifferent types of obsessions and compulsions may provide signif-icant benefits in the future for obsessionality research in epilepsy.

Antiepileptic drugs are another factor to consider because theymay play a role in susceptibility to the development of psycho-pathological syndromes. In this study, most of the patients withTLE were on carbamazepine, whereas most of those with IGE wereusing valproate. There is no evidence that these two AEDS have dif-ferent activities in OCD. Therefore we can conclude that AEDsprobably do not have a strong effect on the difference in psychiat-ric comorbidity rates observed between the two epilepsy groups inour study.

In our study group, only one of the patients with OCD had a for-mer diagnosis and received psychiatric treatment before the studyassessment. Although some other patients were being treated withantidepressants, they thought that their only psychiatric diagnosiswas depression. Anxiety disorders may be underdiagnosed in pa-tients with epilepsy because neurologists may be less likely toask about anxiety relative to depression. Although most of theattention has been focused on depression comorbidity, our resultsconfirm the need to carefully evaluate patients with epilepsy, per-haps especially patients with TLE, for anxiety disorders.

Comorbid depression is common in OCD and complicates itstreatment. In the current study, most of the patients with epilepsywith full or subsyndromal OCD also had a depressive disorder. Itcan be speculated that limbic system involvement may play a rolein this ‘‘dual” psychiatric comorbidity, suggesting that patientswith epilepsy diagnosed with major depression should be carefullyassessed for OCS, and if found, comorbid conditions should be trea-ted simultaneously.

Our study has several limitations. First, small sample size mayhave limited our ability to detect statistically significant differ-ences between the study groups. Second, our sample consisted ofpatients admitted to a tertiary-level epilepsy clinic, and there is apossible bias due to selection of patients with drug-refractoryTLE. The strengths of the current study include the use of a struc-

tured clinical interview to establish psychiatric diagnoses andstructured detailed evaluation of cases of epilepsy to outline inter-mediate cases, with detailed psychiatric interviews conducted bytrained psychiatry professionals.

In conclusion, OCD and depression are common in epilepsy. It iscrucial to recognize and treat these conditions in patients with epi-lepsy. To gain a better understanding of the associations of epi-lepsy with these comorbid conditions, more studies on theneurostructural–clinical correlations are required.

Acknowledgments

We thank Serra Sencer, M.D., for her contributions for the MRIdata, and Sevda Ozel, Ph.D., for her support with statisticalanalyses.

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