Insight in obsessive-compulsive disorder: conception, clinical characteristics, neuroimaging, and treatment

Abstract Obsessive-compulsive disorder (OCD) is a chronic disabling disease with often unsatisfactory therapeutic outcomes. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) has broadened the diagnostic criteria for OCD, acknowledging that some OCD patients may lack insight into their symptoms. Previous studies have demonstrated that insight can impact therapeutic efficacy and prognosis, underscoring its importance in the treatment of mental disorders, including OCD. In recent years, there has been a growing interest in understanding the influence of insight on mental disorders, leading to advancements in related research. However, to the best of our knowledge, there is dearth of comprehensive reviews on the topic of insight in OCD. In this review article, we aim to fill this gap by providing a concise overview of the concept of insight and its multifaceted role in clinical characteristics, neuroimaging mechanisms, and treatment for OCD.

The etiology of OCD is extr emel y complex, involving social, psycholog ical, and biolog ical factors.Ho w e v er, the fundamental pathogenesis of OCD remains unclear, complicating treatment.Prolonged OCD can significantly affect the daily lives and social functions of individuals (Thorsen et al., 2018 ).Current Canadian clinical practice guidelines recommend selective serotonin reuptake inhibitors (SSRIs) and cognitive behavioral therapy (CBT) as the first-line treatments (Katzman et al., 2014 ).Despite the primary reliance on medications in OCD treatment, specific drugs ar e lac king, and some av ailable medications r esult in intoler able side effects.Consequently, 40-60% of OCD patients poorly respond to serotonin reuptake inhibitors (SRIs), and about tw o-thir ds of those who switch to another SRI fail to achieve optimal therapeutic outcomes (Pallanti et al., 2002 ;Pallanti and Quercioli, 2006 ).Numerous studies have demonstrated that the role of CBT, a prominent psyc hother a py tec hnique, in OCD tr eatment.Some e v en argue that CBT may surpass medical treatment in efficacy (Ost et al., 2015 ), with r esponse r ates of 85% in both adults and c hildr en (Storch et al., 2009 ).Howe v er, widespr ead use of CBT is limited, especially in low-and middle-income countries, due to a shortage of trained psychotherapists for OCD.Moreover, the effectiveness of CBT can be hindered by patients' lack of motivation, compliance , mental consciousness , cognitive abilities and insight, and famil y cooper ation (Knopp et al., 2013 ).In addition, about 75% OCD Figure 1: Obsessi ve-compulsi ve and related disorders .T he obsessi ve-compulsi ve and related disorders chapter in the DSM-5 adds four items including substance/medication-induced obsessi ve-compulsi ve and related disorder, other specified obsessi ve-compulsi ve and related disorder, as well as hoar ding disor der and excoriation (skin-picking) disor der.
patients have comorbid conditions such as depression, bipolar disor der, anxiety, eating disor der, substance abuse, Tourette syndr ome, sc hizophr enia, and OCD-r elated disorders (Choi, 2009 ).These comorbidities not only interact with OCD but also significantly affect its treatment efficacy (He, 2017 ).While ov er all OCD tr eatment is effectiv e, individual r esponses v ary gr eatl y, and r esidual symptoms, easy r ecurr ence, and pr olonged courses of the illness can negative affect patients' quality of life and social functioning (Yazici and P er cinel, 2015 ), as well as increase the economic burden of treatment (Strouphauer et al., 2023 ).
According to the DSM-5 diagnostic criteria, some OCD patients may lack insight into their condition, broadening the scope of OCD diagnosis.DSM-5 clarifies that the absence of insight or the presence of delusional beliefs should be categorized as OCD or a r elated disorder r ather than a psyc hotic disorder (Gnanavel and Robert, 2013 ).Pr e vious study has indicated that OCD patients with poor insight often experience more severe symptoms, exhibit poor er r esponses to medical tr eatment, face gr eater impairment in their social functioning leading to increased unemployment (Macy et al., 2013 ), and impose additional economic and social burdens on their families and society (Hollander et al., 2016 ).Appr oximatel y 13-36% of OCD patients lack insight (Manarte et al., 2021a ), exacerbating the disease se v erity and complicating tr eatment and the social burden.Consequently, enhancing the insight of OCD patients is crucial to address the limitations of OCD therapy (Inanc and Altintas, 2018 ).
In summary, while studies have underscored the importance of insight in OCD patients, there is currently a lack of comprehensiv e integr ation of these liter atur es .In this article , we aim to bridge this gap by providing a comprehensive review encompassing the clinical c har acteristics of OCD insight, neur oima ging mec hanisms, and pr ogr ess in the tr eatment of OCD (Fig. 2 ).

Concept of insight
The define of insight has long been contr ov ersial.One widel y acce pted perspecti ve in both clinical and scientific field involves patients becoming aware of their mental health issues, recognizing that these experiences are abnormal and r equir e pr ofessional treatment (Da vid, 2020 ).T his concept comprises thr ee cor e components: (i) understanding the nature of the disease itself; (ii) the ability to identify the associated symptoms; and (iii) treatment adher ence, as pr oposed by David.Importantl y, this concept a pplies to many psychiatric disorders (David, 2020 ).
Ho w e v er, not all patients a gr ee with this viewpoint, some argue what is termed "insight" a mer el y amounts to a gr eeing with the doctor's opinion, which they perceive as cognitiv el y unjust, discriminatory, and exclusionary to w ar d kno wledgeable individuals and their autonomy, infringing on their right to self-determination and self-expression (Slade and Sweeney , 2020 ).Consequently , they advocate for the use of trauma-informed methods and a mental health system that responds to individuals' extreme experiences by listening and exploration rather than negating the reality of their experiences .Con v ersel y, some individuals at risk of mental health issues gener all y accept definition of insight and are willing to r eceiv e "psyc hiatric emer gency services" wher e tempor ary decisions are made by a psychiatrist acting as an agent.Future research could explore the possibility of involving both professionals and individuals with specific mental disorders in clinical inter pr etation of insight.This a ppr oac h aims to ac hie v e a consensus thr ough objectiv e e v aluation, ther eby pr oviding better services for patients.
Research on the relationship between insight and mental illnesses began about 30 years ago (David, 2020 ).Howe v er, during that time, a Lancet editor commented on this r esearc h as "academically meaningful but clinically meaningless."Currently, as more r esearc h has been conducted, se v er al highl y r eliable and effectiv e e v aluation methods hav e emer ged (Bec k et al., 2004 ;Ka plan et al., 2006 ).For example, a conceptual anal ysis r e vie w suggests that insight is best regarded as a mental state, independent of any specific disease, rather than as a symptomatic dimension of the disorder (Mark ov a et al., 2009 ).Furthermor e, a set of reliable tools were used to analyze the correlation of insight with compliance and prognosis (Lincoln et al., 2007 ;Noordraven et al., 2016 ).In general, a good insight in patients has a more significant impact on prognosis than treatment compliance (Lincoln et al., 2007 ).In recent years, with the advancement of the field of "metacognition," Beck et al. ( 2004 ) introduced a novel concept known as cognitive insight.Cognitiv e insight r efers to a cognitiv e pattern wher e individuals challenge their own thoughts , beliefs , and beha viors .A long-term follow-up study involving patients with first-onset mental illnesses found that those with better insight experienced fewer symptoms (O'Connor et al., 2017 ).This suggests that recognizing and enhancing insight are crucial aspects of mental health treatment.

Clinical c har acteristics of OCD pa tients with poor insight
Insight with regards to OCD typically refers to the accuracy of beliefs or rationality concerning compulsions influenced by obsessions (Leckman et al., 2010 ).It primarily manifests as individuals being aware that their obsessions and compulsions are symptoms of OCD.For OCD patients with poor insight, they tend to belie v e that their OCD beliefs are likely or entirely true.Approximately 13-36% of OCD patients fall into this category (Jacob et al., 2014 ).Nearly two decades ago, in an effort to alert clinicians to the range of insights observed in OCD patients and to explore the relationship between insight and other aspects of psychopathology and treatment, it was suggested that a "poor insight" subtype should be included in the DSM, fourth edition (DSM-IV) field trial (Foa et al., 1995 ).It was not until a decade ago that the DSM-5 officially recognized a spectrum of insight in OCD, including patients with poor insight (Gnanavel and Robert, 2013 ).Insight has been recognized as an important clinical feature of OCD (Nissen and Parner, 2018 ), and may serve as predictive factor for successful treatment (Garcia et al., 2010 ).Studies hav e r e v ealed specific clinical c har acteristics associated with OCD patients with poor insight, including an early onset of disease (Fontenelle et al., 2013 ), a prolonged course (Fontenelle et al., 2010 ), and a high rate of family history of OCD (Catapano et al., 2010 ).Insight has been found to be positiv el y associated with age, and younger patients tended to have lo w er le v els of insight (Lewin et al., 2010 ).The de v elopment of insight gener all y emer ges along with the emergence of abstract thinking and formal operations during growth (Zetlin and Turner, 1985 ).
The pr e v alence of c hildhood OCD is ∼1-4% (Millet et al., 2004 ;Zohar, 1999 ), which may be linked to multi-domain impairments, including issue related to insight.This suggests that addressing poor insight, especially in younger children, is crucial for early recognition and treatment.
Furthermore, OCD patients with poor insight often exhibit a high le v el of the contamination/cleaning dimension (Cherian et al., 2012 ;de Avila et al., 2019 ), symmetry/ordering/counting dimension (Hazari et al., 2016 ;Jakubovski et al., 2011 ), and hoarding dimension (de Avila et al., 2019 ;Fontenelle et al., 2013 ).These associations suggest that insight le v els may aid in distinguishing OCD subtypes (de Avila et al., 2019 ).Ho w e v er, ther e is no unified conclusion on whether insight has a relationship with different biological and pr edictiv e v alidities acr oss differ ent dimensions of OCD (Mark ov a et al., 2009 ).For the other side, studies have indicated specific correlations between insight and the se v erity of symptoms with the same dimension (de Avila et al., 2019 ).For example, OCD patients with poor insight trend to hav e mor e se v er e symptoms, as reflected by higher and factorial scores on the Yale-Br own Obsessiv e-Compulsiv e Scale (Y-BOCS) (de Avila et al., 2019 ).Ev en after compr ehensiv e tr eatment, patients with poor insight tr end to hav e a lo w er reduction in their Y-BOCS score and relativ el y poor ther a peutic outcomes (Raffin et al., 2009 ;Selles et al., 2020 ).This lack of insight often results in OCD patients failing to recognize the pathological nature of their obsessions and compulsions, leading them to invest less effort in resisting their symptoms, ultimatel y r esulting in mor e se v er e symptoms and impairments.
In clinical pr actice, neur oleptic medications ar e fr equentl y used for patients with poor insight (de Avila et al., 2019 ) suggesting that these patients may have dysfunction in dopaminergic neural Combining an atypical antipsychotic with SSRIs may exert a synergistic effect by enhancing ser otoner gic activity or combining their r espectiv e mec hanisms of action to str engthen the dopaminer gic neur al cir cuits inv olved.In addition, patients with poor insight may exhibit more severe symptoms, sometimes even r eac hing a par anoid degr ee, whic h leads psyc hiatrists to consider using neur oleptics (Ha gen et al., 2017 ;Tonna et al., 2016 ).Howe v er, e v en with the use of second-generation neuroleptics such as Risperidone and Aripiprazole to potentiate treatment, the effectiv e r ate for r efr actory OCD r emains at onl y ∼40-55% (Albert et al., 2016 ).Studies have also shown that OCD patients with poor insight often have low le v els of empathetic concern and a reduced ability to recognize emotional states, especiall y negativ e emotions (Manarte et al., 2021a ).This may explain why OCD patients with poor insight experience more severe symptoms of depression and anxiety (Altintas and Taskintuna, 2015 ), a higher propensity for suicide tendency, and comorbidities of major de pressi ve disorder (Fontenelle et al., 2013 ), dysthymia (Raffin et al., 2009 ), bipolar disorder, and post-traumatic stress disorder (de Avila et al., 2019 ).Furthermore, OCD patients with poor insight often exhibit ina ppr opriate perception, particularl y in visual and tactile perceptions .T his often indicates that a poor ther a peutic outcome may be linked to specific neurobiological factors and poor insight (Moritz et al., 2018 ;Shavitt et al., 2014 ).Studies have shown that the se v erity of perception abnormalities is positiv el y corr elated with the ov er all se v erity of OCD symptoms (Moritz et al., 2018 ).Ina ppr opriate perception plays a significant role in inducing compulsions in ∼65% OCD patients (Ferrao et al., 2012 ).Abnormal perception can increase the subjective reality of obsession (Jakubovski et al., 2011 ), thus exacerbating the difficulty in changing or resisting these symptoms (Moritz et al., 2018 ) (Table 1 ).
Fr om the neur opsyc hological aspect, OCD patients with poor insight often exhibit poorer verbal memory and executive function (Kitis et al., 2007 ;Tumkaya et al., 2009 ).While there is debate r egarding v erbal memory impairment, some r esearc hers ar gue that OCD patients have impaired "organizational strategy" rather than verbal memory (Chamberlain et al., 2005 ), suggesting that the cognitive deficits in OCD patients with poor insight are related to more complex executive function (Manarte et al., 2021a ).Executive function includes various cognitive processes, including working memory , cognitive flexibility , behavioral cognitive control, attention, self-control, and self-regulation of actions .T hese executive functions r el y on a neur al netw ork inv olving the pr efr ontal cortex, striatum, and cerebellum, with the pr efr ontal cortex being the pri-mary structure (McDougle et al., 2021 ;Tian et al., 2020 ;Wilson et al., 2021 ).In the follo wing section, w e further discuss neur oima ging changes in OCD patients with poor insight, aiming to provide valuable pathways for the treatment of the disorder.

Neur oimaging c hanges rela ted to OCD insight
Recent advancements in brain imaging technologies, particularly ma gnetic r esonance ima ging (MRI), hav e facilitated numer ous neur oima ging studies focusing on brain abnormalities in psychosis with poor insight, especially OCD.These studies have rev ealed structur al abnormalities, with most identifying irregularities in fr ontal, tempor al, and parietal r egions (Cooke et al., 2008 ;Buchy et al., 2017 ;Orfei et al., 2017 ).Functional neur oima ging r esearch has also demonstrated that insight is associated with functional abnormalities in both medial and lateral frontal, temporal, and parietal regions (Raij et al., 2012 ;van der Meer et al., 2013 ;de Vos et al., 2015 ).Mor eov er, poor er insight has been correlated with reduced white matter volume across the brain and diminished gray matter volume in the frontal gyri (Pijnenborg et al., 2020 ).
Man y studies hav e r eported br ain functional and structur al changes in OCD patients (Bourne et al., 2012 ;Diwadkar et al., 2015 ;Posner et al., 2014 ).Our recent study has identified a significant relationship between brain function and the se v erity of obsessions, as well as between br ain structur e and the se v erity of compulsions in individuals with OCD .(T ang et al., 2023 ).Ho w e v er, the neurology of OCD insight remains less explored.Early studies indicated that OCD patients with poor insight exhibited greater structur al br ain abnormalities (Aigner et al., 2005 ) and mor e pr onounced neurologic soft signs, suggesting more extensive neur ode v elopmental abnormalities (Kar ada g et al., 2011 ).Ho w e v er, these studies identified only specific br ain r egions, including the basal ganglion region, parietal lobe (Aigner et al., 2005 ), and the temporal lobe (Fan et al., 2017a ).Recent r esearc h had extended the scope to include the cortical structur e, suc h as cortical thickness and local gyrification index, as well as brain networks in insight investigations (Liu et al., 2019 ).Notably, reduced cortical thickness in the dorsal medial prefrontal cortex, left anterior cingulate cortex (ACC), and right lateral parietal cortex was observed in OCD patients with poor insight compared to those with good insight (Liu et al., 2019 ).Reduced cortical thic kness, r epr esenting a reduction in neurons within cortical columns , ma y reflect insight-r elated c hanges (Kar ada g et al., 2011 ).OCD patients tend to hav e hyper activ e err or-monitoring functions, leading to slo w er decision-making and delayed response to errors, known as "posterror slowing."The medial prefrontal cortex, a k e y player in the error monitoring in OCD patients (Modirrousta et al., 2015 ), further supports the involvement of frontal lobe dysfunction in executive function in OCD patients with poor insight.Additionally, the ACC and orbitofrontal cortex (OFC) in the frontal lobe play r oles in executiv e function in OCD patients (Manarte et al., 2021b ).A study found a negativ e corr elation between the insight score on the Y-BOCS and local gyrification index of the left OFC and left ACC (Venkatasubramanian et al., 2012 ).The ACC, a subcortical structure in the frontal lobe, is probably a high-level regulatory region for emotional information processing and behavioral planning and execution (Bush et al., 2000 ;P alomer o-Galla gher et al., 2008 ), with the dorsal ACC primaril y involv ed in the cognitive function of error monitoring (Bush et al., 2000 ).
Self-enhanced behavioral monitoring is considered an endophenotype of OCD.A 12-year follow-up study r e v ealed that c hildr en with high le v els of observ ational behavior al monitoring were twice as likely to develop OCD compared to a control group (Gilbert et al., 2018 ).This heightened behavioral observation was associated with a r elativ el y smaller ACC volume on the right dorsal side (Gilbert et al., 2018 ), suggesting that the ACC plays a crucial role in modulating behavioral flexibility in response to changing environments (D 'Cruz et al., 2011 ).This finding provides further insight into abnormalities observed in the ACC and LGL in OCD patients with poor insight.As part of the frontal lobe, the OFC contributes to executive function and is vital for human recognition, enhancing the learning pr ocess, and pr ocessing emotions.Ov er activ ation of the OFC can lead to the emergence of repetitive thoughts (obsessions).OCD patients employ compulsions to alleviate anxiety and fear arising from the obsessions, with this re petiti ve behavior associated with the corpus striatum (Saxena and Rauch, 2000 ).Abnormal insight in schizophrenia and other psychiatric disorders is linked to defects in the medial OFC (Shad et al., 2006 ).In summary, the fr ontal cortex, likel y thr ough its involvement in executive function, plays a significant role in OCD insight.The parietal lobe, particularly lesions in the right hemisphere, has been associated with anosognosia (i.e.lack of awareness of neurological deficit symptoms) (Bisiach et al., 1986 ). Research conducted on schizophrenic patients with poor insight has reported that there is a decrease in the density of oligodendrocytes in the inferior parietal leaflet and reductions in the volume or thickness of the prefrontal and parietal lobes, which is associated with decreased self-reflective ability (i.e.cognitive insight).These findings suggest that alterations in brain regions involved in self-reflection and metacognition, such as the medial frontal and inferior parietal lobes , ma y pla y a role in the pathophysiology of poor insight in disorders such as schizophrenia.This insight could potentially be applicable to understanding obsessi ve-compulsi ve internality as well, given the shar ed featur es of insight-r elated abnormalities across these disorders (Buchy et al., 2016 ;Liu et al., 2019 ;Orfei et al., 2013 ).
Considering the fluctuating nature of insight (Abramowitz and J acob y, 2015 ), functional MRI might hold mor e pr omise than structural MRI in revealing this process.Compared with OCD patients with good insight, those with poor insight exhibited dea creased amplitude of lo w-frequenc y fluctuation in the middle temporal gyrus and superior temporal gyrus (Fan et al., 2017b ).The temporal lobe primarily participates in language processing, social perception, and semantic memory, and it is especially sensitive to information related to social r ele v ance or significance (Hoekert et al. , 2008 ;K umari et al., 2010 ).Difficulties in transforming ex-periences into memories may hinder the assimilation of corrective information, contributing to the persistence of poor insight.A study on brain networks found that the functional connectivity between the anterior insula and right medial OFC was reduced in OCD patients with poor insight, and this reduction was negativ el y correlated with the level of insight (Fan et al., 2017a ).Abnormal connectivity between the right anterior insula and right medial OFC mediated the poor insight in OCD, suggesting that impaired ability to encode and integrate self-assessment information (Fan et al., 2017a ).In addition, r esearc h based on a small world model demonstrated a significant reduction in the length of theta wave paths in OCD patients with poor insight (Lei et al., 2017 ).This reduction may disrupt the balance of the small-world model network, leading to dissatisfaction with brain network topology and affecting the functional integration of theta waves in the brain network (Lei et al., 2017 ).The theta wave is known to play a role in working memory (Lisman, 2010 ).As a result, OCD patients with poor insight often exhibit more pronounced defects in working memory (Kashyap et al., 2012 ).Consequently, patients may persist in maintaining irrational beliefs, including the belief that their OCD symptoms are rational and appropriate (Kashyap et al., 2012 ).For example, patients with poor insight may persist in believing that their OCD symptoms are rational and appropriate.
In summary, OCD patients with poor insight appear to exhibit mor e extensiv e cortical abnormalities , in volving the frontal, temporal, and parietal lobes.Previous studies on insight in sc hizophr enic patients have also shown that abnormal changes in the fr ontal, parietal, and tempor al lobes ar e associated with poor insight (Buchy et al., 2017 ).T hese illnesses , including anosognosia, shar e structur al similarities r elated to insight-r elated abnormalities, suggesting a common anatomical basis for poor insight in these conditions.

Relationship between insight and treatment
Treatment of OCD encompasses psychotherapy, pharmacothera py, and physiother a py (mainl y r eferring to a neur omodulation tec hnique).Figur e 3 shows an OCD tr eatment algorithm.Conv entional tr eatments, suc h as psyc hother a py and pharmacother a py, hav e demonstr ated effectiv eness in enhancing the insight of OCD patients to a certain extent.CBT is a first-line treatment for OCD, and many studies have shown its efficacy in improving insight (Matsunaga et al., 2002 ;Selles et al ., 2020 ).Contrary to gener all y accepted views on adult OCD, CBT treatment has shown no impact on baseline insight in pediatric OCD patients .T his suggests that CBT is equally effective regardless of whether or not young patients recognize the excessive, impractical, or obsessive nature of their beliefs (Selles et al., 2020).Additionally, mindfulness-based cognitiv e ther a py (MBCT) has pr ov en beneficial for enhancing insight in OCD patients (Landmann et al., 2019 ).Mindfulness and acceptance-based strategies have been found to reduce pain associated with intrusive thoughts (Marcks and Woods, 2005 ;Najmi et al., 2009 ), increase a patient's willingness to experience intrusive thoughts (Marcks and Woods, 2007 ), and alleviate postexposure anxiety and impulsive behaviors (Catapano et al., 2001 ).With respect to medical treatment, research indicates that poor insight can predict the therapeutic efficacy of SSRIs for OCD.Howe v er, while OCD symptoms and insight do impr ov e some extent after treatment, the effect remains limited (Alonso et al., 2008 ;Catapano et al., 2001 ).Consequently, clinicians often turn to neuroleptics in the treatment of OCD patients with poor insight (de Avila et al., 2019 ).Second-generation neuroleptics such as Risperidone and Aripiprazole can potentiate the ther a peutic effect in improving the insight in some patients, although their effectiveness in treating refractory OCD patients ranges from 40 to 55% (Albert et al., 2016 ).Mor eov er, structur al abnormalities (Zhong et al., 2019 ) and altered functional connectivity (Viol et al., 2020 ;Yang et al., 2015 ) in r elated br ain ar eas partiall y r estor ed in OCD patients after treatment.This suggests that OCD treatment not only ameliorates symptoms but also affects the neurophysiology of relev ant br ain ar eas.
In r ecent years, v arious non-inv asiv e neur omodulation tec hnologies, such as transcranial magnetic stimulation (TMS), including re petiti ve TMS (rTMS) and deep TMS (dTMS), as well as transcr anial dir ect curr ent stim ulation (Saba et al., 2015 ), have gained extensive use in treating a series of mental and neurological disease by regulating neural activity and plasticity (Matsumoto et al., 2010 ;van den Heuvel et al ., 2009 ).Neuromodulation fundamentally aims to restore abnormal insight to the normal le v el by modulating abnormal brain function in OCD (Bais et al., 2014 ;Del et al., 2011 ).Studies have shown that rTMS can contribute to improving a patient's insight (Dlabac-de et al., 2015 ;Tateishi et al., 2019 ).According to the 2019 edition of the Harvard South Shore Pr ogr am for OCD treatment, if the second-generation neuroleptics and other synergistic drugs ar e ineffectiv e, highl y safe and non-inv asiv e neur omodulation tec hniques suc h as TMS can be considered in the next step, potentiall y ele v ating the priority of treatment to node 5 (Beaulieu et al., 2019 ).Compared with medi-cal tr eatment, compr ehensiv e tr eatment involving the combination of medical treatment, CBT, and rTMS targeting the left frontal lobe has demonstrated the ability to enhance insight in OCD patients, especially those with low baseline scores on the Brown Assessment of Beliefs Scale (Huang et al., 2022 ).In addition, transcr anial dir ect curr ent stim ulation tar geting the bilater al supplementary motor area has shown potential in improving OCD insight, with its effects not correlated with reductions in Y-BOCS scores (Harika-Germaneau et al., 2020 ).To target deeper subcortical structures and larger brain volumes, dTMS has been purposed to stimulate the medial prefrontal cortex and ACC: core regions that are associated with insight in OCD.While there is no direct evidence showing that dTMS improves OCD insight, the study has indicated that dTMS applied to the medial pr efr ontal cortex-ACC significantl y impr ov es Y-BOCS scor es in OCD patients who failed to respond to medical treatment (Carmi et al., 2018 ).In addition, r esearc h suggests that high-fr equency (20 Hz) dTMS is mor e effectiv e in tr eating OCD symptoms compar ed to lowfrequency dTMS (1 Hz).Deep brain stimulation (DBS) is an invasiv e physiother a py for psyc hosis (Geor gie v et al., 2021 ).A metaanal ysis has demonstr ated that DBS can significantl y alle viate compulsion, depression, and anxiety symptoms in OCD patients who do not respond to medical treatment (Cruz et al., 2022 ).This impr ov ement may be linked to the fact that cognitive dysfunction is a common adverse reaction to DBS.At present, there is limited r esearc h on the corr elation between stim ulation tec hnologies and insight, which could be an interesting field for future r esearc h.

Summary and perspectives
OCD is a c hr onic illness that can significantly affect a patient's social functioning and cause marked distress .P oor insight in patients is a crucial factor complicating the treatment of OCD.In clinical pr actice, insight serv es as a vital metric for assessing the pr ogr ess of mental illness treatment and plays a pivotal role in consolidating ther a peutic effects and pr e v enting r ecurr ence.Although the conventional clinical definition of insight has been accepted by the public, some patients may perceive it simply as a gr eeing with their doctor's opinion.Ho w e v er, patients often bring their own biases rooted in their experience and knowledge, necessitating a fresh perspective in the concept of insight.From this perspective, insight is not a matter of presence or absence, or even a continuous spectrum.On the contr ary, it r epr esents a process of constructing personal meaning, which is limited over time by cultur e factors.A pr ofound understanding of this concept empo w ers healthcar e pr oviders to better addr ess a patient's extr eme experience thr ough activ e listening and explor ation, a crucial aspect of effective disease treatment.Insight holds great importance in promoting treatment compliance.In the future, adopting a bottomup a ppr oac h (i.e.fr om life experience to theory) or engaging mental health professionals and patients collaboratively in narratives related to specific mental illness could prove advantageous.Starting with empathetic listening and understanding of patients' experiences can substantially enhance treatment compliance.
Most studies concur that OCD patients with poor insight tend to exhibit early onset, a protracted disease course, severe symptoms, a family history of OCD, and a high prevalence of comorbidities.Pr esent r esearc h suggests that insight may be linked to the contamination/cleaning, symmetry/ordering/counting, and hoar ding dimensions.Ho w e v er, consensus r emains elusiv e on dimensions related to poor insight.It is imper ativ e to expand sample sizes and compr ehensiv el y assess drug-naiv e OCD patients at the onset.OCD patients with poor insight often coincide with distorted perceptions, highlighting that subjective reality of obsession and diminishing resistance to abnormal obsessions and compulsions.Such patients frequently exhibit cognitive biases, potentiall y r eac hing par anoid ideation, whic h explains the common use of neuroleptics in clinical practice.
In the diagnosis of mental illnesses such as OCD, it is crucial to rule out physical diseases with medical imaging techniques such as MRI.Additionally, patients often voluntarily undergo these procedures to understand the root causes of their mental health concerns .T her efor e, patients voluntaril y participating in the MRI examinations promote the blossoming of neur oima ging r esearc h.Neur oima ging studies have consistently implicated v arious br ain r egions, primaril y the fr ontal, tempor al, and parietal lobes, in the context of insight in OCD.These findings align with the involvement of k e y br ain r egions, including medial pr efr ontal cortex, ACC, and OFC, belonging to the critical corticostriato-thalamo-cortical circuit: a fundamental model for understanding OCD pathophysiology.Many studies have reported fine structur al c hanges in the cortico-striato-thalamo-cortical circuit, including alterations in gray matter volume (Rotge et al., 2010 ) and functional abnormalities (Posner et al., 2014 ;Zhang et al., 2017 ).These br ain r egions play pivotal r oles in memory, emotional r egulation, and cognitiv e pr ocesses .T heir abnormalities often underlie the genesis of obsessions and the re petiti ve nature of symptoms (van den Heuvel et al ., 2009 ;Nakao et al., 2014 ).Psyc hother a py, pharmacother a py, and physiother a py hav e shown the potential to impr ov e the insight of OCD patients (Huang et al., 2022 ;Landmann et al., 2019 ;Tateishi et al., 2019 ;Selles et al., 2020 ).Compr ehensiv e tr eatment, combining medical tr eatment with CBT and rTMS targeting the left frontal lobe, has proven effective in enhancing OCD insight (Huang et al., 2022 ).Importantl y, tr eatment outcomes ar e notably superior in patients with improved insight compared to those with poor insight (Huang et al., 2022 ).Ther efor e, enhancing insight in OCD patients can not only boost treatment efficacy but also enhance social functioning, alleviating the burden on families and society at large.With the advancements in physiother a py and imaging technology, future research should intensify efforts to identify brain regions and circuits associated with insight, facilitating pr ecise neur omodulation tr eatments.Some sc holars hav e proposed that, as OCD patients' stimulation targets are variable, selecting physiother a py based on the specific symptom pr ofile can activ ate fr ontal cortex r egions mor e effectiv el y (Barcia et al., 2019 ;Janssen et al., 2022 ).Future endea vors ma y in volv e lar ger-sample cohort studies, allowing for precise, individualized physiother a py plans tailored to demographic data, clinical symptoms, and MRI findings .In recent years , go vernments worldwide and scientists ha ve in vested in R&D inbrain-computer interface,s artificial intelligence, and other cutting-edge technologies.These advancements hold the promise of creating more intelligent physical thera pies.offering r ene wed hope for patients with OCD and other refractory mental illnesses.

Figure 2 :
Figure 2: Ov er all discov ery of the insight effect for OCD.

Table 1 :
Characteristics of OCD patients with poor insight.