Defined broadly, executive functioning includes a number of processes focusing on flexibility and goal-directed behavior, and is largely thought to occur in the prefrontal cortex (Baddeley, 1986; Lezak, 1995). Aspects of executive functioning include attentional control, cognitive flexibility, and goal setting.

Christensen et al. (1992) examined executive functioning and OCD in a sample of 18 OCD participants matched for age, gender, and education with 18 control participants. In this study, participants completed the Wisconsin Card Sorting Test (WCST; Heaton, 1981), executive verbal and nonverbal subtests of the Wechsler Adult Intelligence Scale (WAIS-R; Wechsler, 1974), verbal fluency, tactual performance, and motor functioning tests. Results indicated that OCD participants performed worse than their matched controls on tests of verbal fluency, tactual performance, and WAIS-R Block Design. All of these tasks involve aspects of nonverbal memory (tactual performance, block design) and tasks where speed contributed to performance (verbal fluency, block design). A significant limitation of this study, along with many other studies examining executive functioning in OCD, is the lack of a psychiatric comparison group. Without these comparison groups, it is difficult to ascertain whether these executive functioning deficits are specific to OCD or if they extend to other areas of psychopathology as well.

Gambini, Abbruzzese, and Scarone (1993) further investigated OCD and executive functioning. Twenty-three OCD participants were matched for age with 27 controls. Participants completed tasks of voluntary saccadic eye movement (VSEM), smooth pursuit eye movement (SPEM), the WCST, and attention. Gambini et al. (1993) found significant differences on WCST total and perseverative error scores, with OCD participants performing poorer than controls. These findings are consistent with Christensen et al. (1992), showing deficits specific to nonverbal information in those diagnosed with OCD. Although participants were matched for age in this study, education levels significantly differed between the two groups, which may have affected the results of the study. However, research by Nelson, Early, and Haller (1993) also supports these findings of impaired nonverbal attention in those diagnosed with OCD.

Abbruzzese, Ferri, and Scarone (1995) found deficits in OCD patients on the WCST. They examined a sample of 33 participants diagnosed with OCD matched for age, sex, and education with an unmedicated group of 14 individuals with OCD as well as with a non-OCD control group. Treated participants were all receiving fluvoxamine. Results indicated that the non-medicated group (after controlling for demographic information) performed poorer than the medicated OCD group on the WCST, committing more total errors and a lower percentage of conceptual level responses. Abbruzzese et al. (1995) did not find significant differences on the WCST between the medicated group and the non-OCD control group. The results suggest that, although medication does not alter functioning of the prefrontal cortex, better performance on tasks of executive functioning may be attributed at least partially to reduced symptoms of OCD (Greisberg & McKay, 2003).

As mentioned before, a notable limitation in the studies discussed to this point is the lack of a psychiatric comparison group. Cohen et al. (1996) attempted to address this gap by comparing executive functioning in OCD patients to patients suffering from another anxiety disorder. This study included 65 participants diagnosed with OCD, 17 participants diagnosed with social phobia, and 32 nonpsychiatric controls. Visuospatial abilities were examined using the WAIS-R Block Design, the Benton Visual Retention Test (BVRT; Benton, 1974), and the Matching Familiar Figures Test (MFFT). Executive functioning was measured using the Trails A and B of the Trail-Making Tasks (TMT; Reitan & Wolfson, 1985), and attention and memory were examined with the WAIS-R Digit Span subtest. Participants in the OCD group performed poorer on tasks of visuospatial abilities than the normal control group but did not perform poorer on tasks of executive functioning.

In another study investigating executive functioning in OCD and other anxiety groups, 30 participants diagnosed with OCD were compared to 30 healthy controls, 20 participants diagnosed with depression, and 30 participants diagnosed with panic disorder (Purcell, Maruff, Kyrios, & Pantelis, 1998). Participants in the control group were matched with the clinical groups according to age, sex, handedness, education, and premorbid intellectual functioning. Using the Cambridge Neuropsychological Test Automated Battery (CANTAB; Robbins, James, Owen, Sahakian, McInnes, & Rabbit, 1994), Purcell et al. (1998) found that, relative to the other three groups, the OCD group showed significantly lower performance on executive functioning tasks examining initiation of tasks and speed of completion. Poorer performance on speed tests has been found in previous studies with OCD patients (Christensen et al., 1992). In other areas of executive functioning, OCD participants did not differ from the other groups.

Cavedini, Ferri, Scarone, and Bellodi (1998) further examined differences in executive functioning in OCD patients and other psychiatric groups. In this study, they compared a sample of 28 OCD participants with a sample of 29 individuals diagnosed with major depression. A sorting test, a verbal fluency test, the WCST, and the Object Alternation Task (OAT; Pribram & Mishkin, 1956) were used to measure executive functioning. While depressed participants performed poorer on tests of verbal fluency and sorting, OCD participants made more perseverative errors on the OAT. According to this study, executive functioning may be affected in both OCD and depressed individuals, although the particular deficits in executive functioning may differ. On a related note, Moritz et al. (2001) suggests that depressive symptoms in those suffering from OCD may be associated with additional worsening of executive functioning, whereas deficits in OCD may be the result of fundamental features of the disorder.

Another possible contributor to the variation in findings from the studies discussed thus far is the lack of examination of specific OCD subtypes. The studies mentioned have targeted executive functioning in OCD as a whole, but they have not researched differences in executive functioning in subtypes of OCD. Because of the heterogeneity of OCD symptoms, it is possible that different symptomatology may relate to different presentations of executive dysfunction. Hartston and Swerdlow (1999) conducted a study in which differences in OCD subtypes were examined between an OCD group (n  =  76) and a healthy control group (n  =  62). Participants were matched for gender, age, education, marital status, handedness, and employment status. Tasks for executive functioning included a visuospatial priming (VSP) task and a Stroop test. The OCD group performed better than the control group in the VSP task when they were cued to respond to the location of a stimulus in a visual field. In other words, when a stimulus repeatedly occurred in one area, participants in the OCD group were able to respond faster to the stimulus than the control group. This is known as a “facilitation effect.” OCD participants also had more interference errors on the Stroop test compared to the healthy control group. In terms of OCD subtypes, participants with aggressive obsessions, “not just right” obsessions, and checking compulsions, all benefitted greater from the “facilitation effect” in the VSP task.

More recent research in the area of executive functioning and OCD has focused specifically on the task of “set-shifting.” Set-shifting is a type of cognitive flexibility that allows individuals to shift their attention from one stimulus to another based on continuously changing reinforcement contingencies (Monchi, Petrides, Petre, Worsley, & Dagher, 2001). The WCST is often used to test set-shifting. Boldrini et al. (2005) investigated set-shifting in a sample of 25 OCD participants, 15 participants with panic disorder and agoraphobia (PD/A), and 15 healthy controls. Participants did not differ in age or education level, and the investigators controlled for comorbid depression. On the WCST, the OCD group showed deficits in learning from negative feedback to shift sets compared to both the healthy control group and the PD/A group. These results are supported by Bohne et al. (2005), who also found difficulties in learning from feedback on the WCST in an OCD group. While some past research on set-shifting in OCD support the findings from these studies (Lucey et al., 1997; Veale et al., 1996), others contradict them (Abbruzzese, Ferri & Scarone, 1995; Kuelz, Hohagen, & Voderholzer, 2004).

Recent research examining executive functioning and OCD has also utilized functional magnetic resonance imaging (fMRI) technology to study brain activity during these tasks. For example, Nakao et al. (2005) examined brain changes in OCD patients during a Stroop task using fMRI. Ten OCD patients were divided into a medication treatment group (n  =  4) and a CBT group (n  =  6). Nakao and colleagues found increased task-related activation in areas of the parietal cortex and cerebellum in both groups following 12 weeks of treatment. This increased activation coincided with decreased symptoms found on the Yale Brown Obsessive–Compulsive Scale (YBOCS; Goodman et al., 1989). These fMRI findings support previous research that also indicates a relationship between improved symptoms and improved executive functioning tasks (Abbruzzese et al., 1995). In another fMRI study using the Stroop task (Schlösser et al., 2010), OCD patients (n  =  21) were matched with healthy controls (n  =  21) for age and education. Both groups showed activation in the dorsal anterior cingulate (AC), the left ventrolateral prefrontal cortex (VLPFC), and left dorsolateral prefrontal cortex (DLPFC), although the OCD group showed significantly more activation in the dorsal AC and right DLPFC than controls (Table 4.2).

Fitzgerald et al. (2005) compared eight OCD patients to seven nonclinical controls in an fMRI study using tasks that elicited errors. They looked particularly at AC activation, given the role of AC abnormalities often found in OCD patients. The investigators found that while both the OCD group and the healthy control group showed dorsal AC activation during these error tasks, the OCD group showed significantly more activation in the rostral AC, indicating that error processing might occur in different areas in OCD patients relative to healthy controls. As in prior studies reviewed, where greater symptom severity was associated with poorer neurocognitive functioning, there was a positive correlation between symptom severity and activity in the rostral AC.

In another fMRI study, Roth et al. (2007) investigated areas of brain activation in inhibition control. They compared 12 OCD patients and 14 healthy controls on a “go/no go” task. During this task, healthy subjects showed right hemisphere activation in the inferior frontal gyrus, while OCD patients showed more bilateral activation. OCD patients also showed less activation compared to controls in the right hemisphere, including the right inferior frontal gyrus and right medial frontal gyrus. Among OCD patients, symptom severity was negatively correlated with AC and right orbitofrontal cortex activation and positively correlated with thalamic and posterior cortical activity. These findings, along with findings in other fMRI studies (Fitzgerald et al., 2005; Schlösser et al., 2010), are consistent with neurobiological models of OCD that indicate abnormal activity in the fronto-striatal circuit.

In summary, much of the research examining executive functioning and OCD suggests that individuals with OCD show more interference effects (i.e., the Stroop task) than healthy controls or other psychiatric groups, along with deficits in “set-shifting” organizational strategies, especially on tasks such as the WCST (Abbruzzese et al., 1995; Cavedini et al., 1998; Gambini et al., 1993). It also appears that OCD patients may struggle with tasks where speed impacts performance (Christensen et al., 1992; Purcell et al., 1998). In terms of neuroimaging findings, OCD patients exhibit abnormal functioning in areas involved in the fronto-striatal circuit. Most commonly found among these studies is abnormal activity in the AC. Many of these studies also highlight positive correlations between abnormal functioning and symptom severity. Further research in the area is warranted, especially examining differences in executive functioning among OCD subtypes along with the effect of depressive symptoms on OCD and executive functioning (Moritz et al., 2001). Greisberg and McKay (2003) also suggest future research to investigate whether these cognitive deficits improve with traditional psychosocial therapy or medication.

Memory functioning has typically been assessed in comprehensive neuropsychological studies of OCD. It has been hypothesized that memory functioning is impaired in OCD given the pervasive doubting associated with the condition. This could be attributed to real deficits in memory. For example, Christensen et al. (1992) found that OCD participants performed significantly worse on tasks of delayed recall on the Wechsler Memory Scale (WMS; Wechsler, 1945) (Table 4.3).