Group therapy has its origins in psychodynamic models of psychopathology and developed before CBT. In group therapy, it is viewed that group members’ interactions are the tool of change [32]. From the perspective of CBT, it is seen that individuals who have OCD inaccurately interpret situations, objects or thoughts being intrusive as hazardous. By way of cognitive and behavioral treatment strategies, CBT aims at changing/diminishing dysfunctional thoughts that produce anxiety and reducing/replacing behaviors that maintain symptoms [33] [34]. Some studies have proposed that cognitive therapy was an efficient alternative in many cases [35] [36].

In group-CBT, the cognitive-behavioral model given to the group is more than the interaction between the members. It is structured and directive, time-limited and collaborative as in individual CBT [30]. However, group-CBT pays also attention to the therapeutic factors occurring in therapy. Group-CBT encompasses:

1) cognitive restructuring through behavioral experiments,

2) normalizing through identification with others,

3) “in-vivo” exposure, positive reinforcement and vicarious learning in a safe environment,

4) the experience of mastery.

With respect to the effectiveness of CBT, there has been an array of studies. For example, Cabedo et al. [19] compared the efficacy of individual and group cognitive-behavior therapy for OCD treatment. They took into consideration the change in the severity of OCD in both the short and long term. Forty-two individuals having OCD attended the treatment programs and were assigned to group CBT (n = 24, in four groups) or to individual. Sixteen and twenty-two participants completed the treatments. The Y-BOCS were evaluated at pre- and post-treatment and at the one-year follow-up. At post-treatment the individual CBT treatment had higher recovered rate than group CBT and at follow-up the recovery rate decreased to 62.5% in individual CBT and to 31.8% in group CBT. That is, group CBT is effectively decreasing OCD symptoms and one year later the post-treatment changes remained unchanged. The finding that group OCD is less effective than individual CBT for OCD is supported by NICE [37].

Conversely, Çelik et al. [38] have reported that group CBT is decreasing the symptoms of obsessive-compulsive disorder in undergraduate students in Turkey. Along with this, in a 1-year follow-up study the results of CBGT were evaluated. The reduction in symptom severity observed at the end of the treatment was retained during one year. Eleven of forty-two patients relapsed in the follow-up term [39]. The CBGT’s effectiveness is supported by this study but larger and long term-randomized controlled trials are necessary so as to validate this finding.

In a similar context, Haraguchi et al. [23] examined the influence of cognitive-behavioral group therapy (CBGT) on inflated responsibility. The aim of the study was to investigate the effect of CBGT on OCD and beliefs of responsibility. Thirty-six participants who meet the criteria of OCD in DSM-5 (Diagnostical and Statistical Manual of Mental Disorders) were recruited to the group and twenty-eight of them completed twelve sessions. Pre- and post-treatment evaluations were practiced. The results clearly documented that OCD symptoms and responsibility beliefs significantly improved at the end of the treatment. The study points out that CBGT improves both obsessive-compulsive symptoms and inflated responsibility beliefs in individuals who have OCD.

Regarding the severity of CBT and the effects on families, some researchers implemented a study to evaluate the impact of CBGT with the brief involvement of family members on family accommodation (FA) and to define predictors of FA reduction. 98 pairs of patients who have OCD and their family members were assessed. 52 were assigned to the intervention group (12 CBGT sessions) and 46 to a waiting list. FA and symptom severity were evaluated before and after the treatment. Significant improvement of OCD symptoms and FA scores was noted after the intervention in comparison to the control group. The predictors of family accommodation were the variables: patient features—absence of comorbid UPD (unipolar depression), lower obsession score, and higher education level; family member features—higher hoarding score. In the model, 47.2% of the variance was explained in FA scores after the treatment. So CBGT contributed to reducing FA for patients having OCD and the brief involvement of family members. These results can help CBGT protocols to be qualified [40].

Being in the spectrum of OCD, hoarding disorder was also addressed in a study in terms of group-CBT without the clinicians’ home visits. The participants having hoarding disorder engaged in either a 16 or 20 session program of group CBT and 30 (67%) successfully completed treatment. The participants showed noteworthy improvements in hoarding symptoms as well as other symptoms such depression and anxiety. Their quality of life also increased after the treatment [41]. And the findings were comparable to two clinical trials on individual CBT which were published for the treatment of hoarding disorder [42] [43]. The results suggest that CBT group for hoarding disorder may be a cost-effective and practical therapeutic method.

Additionally, a study investigated the effectiveness of group-cognitive behavioral therapy versus SSRIs (fluoxetine) for obsessive-compulsive disorder. According to the conclusion, response rates to both treatments were congruent and lower than reported data in the literature. It may be because of the broad inclusion criteria and the resulting sample being more similar to the real setting [44].

As well as CBT, ERP systemically and deliberately assists the person to get close his/her most feared thoughts or situations and refrain him/her from an activity which intentionally reduces anxiety [13]. Recently, ERP has grown into a valuable option of treatment. Exposure means exposing to stimulus that invokes fear and response prevention describes behavioral avoidance which relieves rituals, compulsions, and behaviors relevant to safety. In Foa and Kozak’s meta-analysis [13], which encompasses 12 ERP studies and 330 OCD patients, it is reported that among patients there is an 83% response rate. However, ERP has high drop-out rates and low-level commitment.

In a pilot study, whether intensive ERP group treatment for OCD was effective was addressed. Six individuals whose OCD symptoms were basically different from each other engaged in the study and they had a long history of OCD, four having the disorder since childhood or early adolescence years. With prolonged exposure training on second and third day, the treatment which was designed as one long session, was conducted for four successive days. All of the patients stated high acceptance for the treatment format, content and protocols. When compared, there were 17.8 points reduction on Y-BOCS between pre- and post-treatment and at follow-up in six months the point just negatively increased 0.6 point [16]. This study implies that intensive group ERP seems to be a promising treatment for OCD and larger studies are also needed.

In a similar vein, Haland et al. [17] carried out a study about the effectiveness of ERP-focused group therapy for patients with OCD, which lasted 12 weeks in a community-based outpatient clinic in Norway. The participants involved 54 patients who have been diagnosed with OCD. The assessment scales were administered before treatment, after treatment and follow-ups ranging from 3 and 12 months. Analyses indicated that the offered group behavioral therapy to OCD patients dramatically improved ratings of OC symptoms along with depression and anxiety. The improvements were retained in both follow ups but the delayed effect of therapy wasn’t observed after 12-month follow-up. The results point out that behavioral group therapy can be delivered to OCD patients as well as comorbid disorders. It can be concluded that this study supports the pilot study performed by Havnen et al. [16].

Another study examined if group-based CBT with ERP is efficient in patients who have OCD. The study involved twenty-four patients having OCD, they were divided into four groups and all participated in every session in group CBT which was designed to continue ten sessions. Each patient completed Y-BOCS and the Maudsley Obsessive-Compulsive Inventory (MOCI) at pre- and post-treatment. The YBOC mean (s.d.) score post-treatment was considerably lower than pre-treatment. But the study had some limitations. It was limited in sample size and the patients were not randomly assigned. Also, the researchers have not collected data on further management [45]. However, it can be gathered from the study that group therapy is a handy way of delivering CBT with ERP especially because of lower drop-out rates.

In one study conducted in Iran, the effects of adding group acceptance and commitment therapy (ACT) to individuals who have been diagnosed with obsessive-compulsive disorder (OCD) were investigated and they were already taking an optimal dose of SSRIs (selective serotonin reuptake inhibitors). The study was performed with forty-six Iranian women, on SSRIs, who were randomized to group ACT + SSRI or continued conditions. SSRI dosages were retained stable throughout the study. The results of the study showed considerable reductions on the Yale-Brown Obsessive-Compulsive Scale Self (Y-BOCS-SR) in both conditions at post-treatment. At follow-up, there were significant reductions in the ACT + SSRI condition when compared to only SSRI treatment. These results demonstrate that group ACT is a fruitful treatment for OCD and a successful alternative to SSRI treatment [31]. However, the study included some limitations that:

· the study was just confined to females,

· the sample size was small,

· there were just two months for follow-up to assess clinical outcomes,

· the study was implemented by self-reporting,

· random assignment and assessments were applied after all participants were on SSRIs.