The subthreshold autistic traits in patients with adult-onset obsessive-compulsive disorder: a comparative study with adolescent patients

I tratti autistici sottosoglia in pazienti con disturbo ossessivo-compulsivo a insorgenza nell’età adulta: uno studio comparativo con pazienti adolescenti


1Department of Psychiatry, Adnan Menderes University, Aydin, Turkey
2Department of Child and Adolescent Psychiatry, Adnan Menderes University, Aydin, Turkey
3Child Diseases and Pediatric Surgery Training and Research Hospital, Department of Child and Adolescent Psychiatry,
Izmir, Turkey
4Department of Child and Adolescent Psychiatry, Pamukkale University, Turkey

SUMMARY. Objective. The primary objective of this study was to compare the adult-onset and adolescent obsessive-compulsive disorder (OCD) patients in terms of the subthreshold autistic traits. Methods. 29 adolescent, and 45 adult-onset OCD patients were assessed by Autism-spectrum Quotient (AQ). Results. The ratio of males to females, the frequency of ritualistic compulsions, and the mean number of lifetime compulsions were significantly higher in adolescents with OCD compared to adult-onset patients. Adult-onset OCD patients had significantly higher scores on total, social skills, attention shifting, and imagination subscales of AQ than adolescent OCD patients. The mean number of compulsions, attention shifting scores of AQ, and female gender significantly predicted the distinction between adolescent and adult-onset OCD patients. In adult-onset patients, there were significant correlations between the mean number of lifetime obsessions and total, social skills, attention switching, communication, and imagination subscale scores of AQ. Conclusions. We suggest that subthreshold autistic traits may play a significant role in the occurence of obsessive-complusive symptoms (OCS) in adult-onset OCD. Autistic traits seemed to be higher and had an closer relationship with the frequency of lifetime obsessions in AO-OCD patients than in adolescent patients.

KEY WORDS: autistic traits, obsessive-compulsive disorder, adolescents, adults.

RIASSUNTO. Scopo. L’obiettivo principale di questo studio è stato quello di confrontare i pazienti con disturbo ossessivo-compulsivo (DOC) dell’adulto e dell’adolescenza in termini di tratti autistici sottosoglia. Metodi. 29 adolescenti e 45 pazienti con insorgenza in età adulta sono stati valutati con l’Autism-spectrum Quotient (AQ). Risultati. Il rapporto tra maschi e femmine, la frequenza delle compulsioni ritualistiche e il numero medio di compulsioni durante la vita erano significativamente più alti negli adolescenti con DOC in confronto ai pazienti con insorgenza in età adulta. Questi ultimi hanno avuto punteggi significativamente più alti su totale, abilità sociali, spostamento dell’attenzione e sottoscale immaginazione di AQ rispetto ai pazienti adolescenti con DOC. Il numero medio di compulsioni, i punteggi in grado di spostare l’attenzione di AQ e il genere femminile hanno previsto in modo significativo la distinzione tra pazienti con DOC in età adolescenziale e adulti. Nei pazienti con insorgenza in età adulta, vi erano correlazioni significative tra il numero medio di ossessioni durante la vita e le abilità totali, di abilità sociali, di cambio di attenzione, di comunicazione e di immaginazione sottoscale di AQ. Conclusioni. L’indicazione è che i tratti autistici sottosoglia possano svolgere un ruolo significativo nella comparsa di sintomi ossessivo-compulsivi nell’ADD a esordio in età adulta. I tratti autistici sembravano essere più alti e avevano una relazione più stretta con la frequenza delle ossessioni della vita nei pazienti con AO-OCD rispetto ai pazienti adolescenti.

PAROLE CHIAVE: tratti autistici, disturbo ossessivo-compulsivo, adolescenti, adulti.

Obsessive-compulsive disorder (OCD) is a heterogeneous neuropsychiatric disorder characterized by recurrent intrusive thoughts and repetitive ritualistic acts. The prevalence of OCD is estimated between 0.5-4% in youngs1,2 and between 2-3% in adults3. Many studies have found that child and adolescent-onset OCD patients had male dominance4,5, more severe and resistant symptoms6-8, a family history of OCD9-11, higher rates of comorbidity with disruptive behavior disorders, attention deficit hyperactivity disorder and Tourette’s syndrome6,9,10,12,13, other anxiety disorders14 than adult-onset OCD. Further, adolescent patients are more likely to present with compulsions15,16, higher rates of aggressive obsessions, and repeating, ordering/arranging and hoarding compulsions14,15 than adult OCD patients.
OCD and autism spectrum disorders (ASD) share similar clinical characteristics, particularly symptoms of repetitive or stereotyped behaviors, inflexibility, the need for sameness17. Repetitive rituals such as ordering, hoarding, touching, or tapping are frequently seen in autism and many of these behaviours are similar to those seen in OCD patients17-20. Autistic-like traits are considered as milder manifestations of psychopathology or as existing at the border between normal and pathological conditions. The presence of restricted repetetive behaviours can be noticed as early as the first 12 months of age who are later diagnosed with ASD21. Autistic-like traits, also named as the “broader autistic phenotype”, include reduced social skills, narrow interests, repetitive rituals, and increased attention to details22. Previous research has shown a high prevalence of autistic-like traits in both children17,18,20,23 and adults with OCD24,25.
Despite some evidence for several clinical differences between juvenile-onset and adult-onset OCD, some uncertainties still exist in demonstrating the importance of autistic traits in adolescent and adult patients with OCD. It is also unlear whether autistic traits among OCD patients are generally elevated across development, or whether they are concentrated in younger samples. Therefore, this study tried to demonstrate that subthreshold autistic traits are not spesific to adolescent OCD patients (A-OCD), but also are associated with adult-onset (AO) OCD. A direct comparison of adolescent and adult-onset OCD may help us to better understand the associations of autistic traits with OCD across two patient groups. The primary objectives of this study were: 1) to compare the adult-onset and adolescent OCD patients regarding the autistic traits; and 2) to investigate the relationships between subthreshold autistic traits and OCD within two age groups. Therefore, comparing the adult-onset and adolescent OCD patients, we hypothesized that the subthreshold autistic traits might also be related to OCD symptomatology in AO-OCD patients as much as or more than in A-OCD patients.
The individuals with AO-OCD (onset age and current age >18 years; n=45), and (A-OCD) (onset age and current age ≤18 years; n=29) who admitted to Adult, and Child and Adolescent Psychiatry Departments were included in the study. The patients were screened by Structured Clinical Interviews for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) Axis I Disorders (SCID-I)26, or Kiddie Schedule for Affective Disorders and Schizophrenia-Present state and Lifetime version (KSADS-PL)27,28. The patients with current and lifetime diagnoses of mental retardation, psychotic disorders, bipolar disorders, alcohol/substance use disorders were excluded from participation. The diagnostic assessment of ASD was made according to DSM-IV-TR criteria for ASD diagnoses such as autism, Asperger’s syndrome, or atypical autism. Detailed information on demographic and clinical features of the sample (age at onset of OCD, gender, the presence of comorbid psychiatric diagnoses) was collected from parents, clinical interviews or retrospective investigation of medical records. We defined age at onset of OCD as the age that the patient, or a family member, remembered as the beginning of the obsessive-compulsive symptoms (OCS). Eighteen participants in adolescent group, and thirty four patients in adult group were under the antidepressant and/or antipsychotic treatment during the assessment. None of the patients were participating in psychotherapy at the time of participation. The study was approved by the institutional review board, and all participants or parents gave their written informed consent before participating.
The severity and content of OCS were determined through the Childhood YaleBrown Obsessive-Compulsive Scale (CBYOCS)29,30 and Yale-Brown Obsessive-Compulsive Scale (YBOCS)31,32. The CYBOCS and YBOCS are semi-structured interviews containing checklists of obsessions and compulsions. Scales assessing the severity of obsessions and compulsions separately (range 0-20) are added to a total score (range 0-40).
Autism symptoms were rated by Autism Spectrum Quotient (AQ)22. The AQ is a self-administrated, 50 item questionnaire designed to quantify autism traits in subjects of normal intelligence. The AQ consists of five subscales each containing 10 items assessing social skill, attention switching, attention to detail, communication, and imagination. Each question demands the participant to indicate the extent to which they agree or disagree with the item. Turkish version of AQ was found to be a reliable instrument in university students 33, and previously used in adolescent studies34,35.
Statistical analysis
The group differences were examined using chi-square, and student’s t test, according to normal distribution. The correlations between several clinical variables of interest were examined with Spearman correlations. A multiple logistic regression analysis was made to determine the associations between the predictors and the dependent variable (adolescent and adult patients with OCD). All statistical assessments were two tailed, and we considered results to be significant at p<0.05. We used SPSS version 22.0 statistical software (SPSS Inc., Chicago, IL, USA) to perform our analyses.
The general description of the adolescent and adult-onset OCD groups are presented in Table 1. As indicated in Table 1, the ratio of males to females was significantly higher in A-OCD group compared to AO-OCD group (p=0.02). The frequency of ritualistic compulsions (p=0.001), and the mean number of compulsions (p<0.0001) were significantly higher in A-OCD patients than in adult patients. AO-OCD patients had significantly higher scores on total (p=0.002), social skill (p=0.03), attention shifting (p=0.004), and imagination (p=0.03) subscales of AQ than A-OCD patients. To determine the variables which would predict the differences between adolescent and adult patients with OCD, six predictors (gender, mean number of compulsions, social skills, attention shifting and imagination subscale scores of AQ, and ritualistic compulsions) were included in a backward multivariable logistic analysis. The final model was found to fit the data adequately (Hosmer and Lemeshow’s  χ 2=5.994, p=0.540). Overall, the model was able to correctly predict 74.6% of the cases. The mean number of compulsions (Exp(B)=0.457, 95% CI: 0.290-0.721, p=0.001), attention shifting scores of AQ (Exp(B)=1.727, 95% CI: 1.198-2.490, p=0.003), and female gender (Exp(B)=0.294, 95% CI: 0.088-0.988, p=0.048) significantly predicted the distinction between adolescent and adult patients with OCD (Table 3).
The correlation analyses indicated that the communication subscale scores of AQ were significantly correlated with both the mean number of obsessions (r=0.48, p=0.007), and compulsions (r=0.40, p=0.02) in adolescent patients (Table 4). In AO-OCD group, there were significant correlations between the mean number of obsessions and total (r=0.33, p=0.02), social skills (r=0.36, p=0.01), attention switching (r=0.31, p=0.04), communication (r=0.37, p=0.01), and imagination subscale scores of AQ (r=0.34, p=0.02) (Table 5).

The main purposes of the present study were to compare the A-OCD and A-OCD patients with respect to subthreshold autistic traits, and to investigate the relationships of autistic traits with OCD within two groups. Comparing adult-onset and adolescent OCD patients, we hypothesized that the subthreshold autistic traits might also be related to OCD symptomatology as much as or more than AO-OCD patients.
Our results demonstrated that A-OCD group had significantly higher proportion of males compared with AO-OCD group, in accordance with some of the studies4,5,12-15,36. Patients with AO-OCD showed a significantly higher proportion of females compared with adolescent patients, consistent with the findings of Dell’Osso et al37 Multiple regression analysis also demonstrated that gender was a strong predictor of adult-onset or adolecent OCD. In this study, age at onset of OCD was not related to the severity of autistic traits within both groups. This finding might indicate that autistic traits have a lifetime and stable course across the patient groups. Autism was traditionally considered as a clinical condition distinct from the general population, but recent evidence suggests autistic traits are continuously distributed across the population from the normal range to the clinical extreme conditions 38-40. Autistic traits appear to be moderately stable from childhood to early adulthood. In this sudy, we also failed to find any significant relationships between the current severity of OCD symptomatology and autistic traits. The high proportion of the patients who were under treatment with antidepressants during the assessment period might partly explain this finding. There is no previous agreement on the specific content of OCS associated with adult-onset and adolescent OCD. In the present study, we have found that A-OCD patients had more compulsions, and higher rates of ritualistic compulsions than those with AO-OCD, in consistent with some of the studies which reported that adolescent subejcts had more compulsions 14,16, and higher rates of aggressive obsessions, and repeating, ordering/arranging and hoarding compulsions14,15 compared to adult OCD patients. Our results also demonstrated that the difference between adult-onset and adolescent OCD patients was significantly predicted by the mean number of lifetime compulsions. This finding is in accordance with some studies which reported that the frequency of compulsions tended to decrease as age increases. Compared to repetitive motor acts and compulsions, which lessen in frequency as an individual gets older, restricted interests and obsessions continue to persist in older populations 21,41-45. Clinical research demonstrate that autistic traits present in both children17,18,20,23 and adults with OCD24,25. In our study, AO-OCD patients displayed more severe autistic traits than adolescent subjects with OCD. Particularly, the traits in social skills, attention shifting, and imagination domains were considerably higher in adult-onset patients than in adolescent OCD patients. Among these traits, attention shifting scores of AQ were found to be the strongest predictor for adult-onset OCD. Similarly, Cath et al.20 reported that the adult patients with OCD and ASD had significantly higher scores on AQ subscale ‘attention shifting’ than the OCD group. In our study, there were also significant differences between two patient groups in terms associations of autistic traits with the mean number of lifetime OCS. In adolescent subjects, the difficulties in communication was found to be significantly correlated with the lifetime frequency of both obsessions and compulsions. In contrast, there were no relationships between the mean number of compulsions and autistic traits within AO-OCD group. However, the all autistic traits except attention to detail displayed significant correlations with the lifetime frequency of obsessions in these patients. These findings might indicate that subthreshold autistic traits in AO-OCD patients had broader and more intense associations with the frequency of obsessions compared to adolescent patients. A previous study 19 found an overall positive correlation between AQ total scores and YBOCS severity scores. Specifically, attention shifting and communication subscales of AQ subscales were significant predictors of OCD symptom severity while the difficulties in attention to detail demonstrated low correlation with OCD symptoms and severity. Attention switching and communication traits were the most important predictors of ‘aggression and checking’, ‘symmetry and ordering’ and ‘contamination and washing’ symptoms. Some studies found several deficits in focused attention, sustained attention, selective attention, attention span, and information processing in comparison to healthy controls 46-48. Clinical symptoms of inattention have been reported especially in pediatric patients with OCD49, and children with OCD have shown deficits in selective and focused attention20,50. Difficulties in the social use of language could be a reliable autistic feature Autism symptomatology in the language and communication domain of impairment can also include a significant delay in the acquisition, comprehension and articulation of speech. Communication with the patient is universally impaired to some degree in autism51.
The small sample size may prevent the generalization of our findings. Further studies in larger samples are required to confirm the results of this study. Another limitation is that retrospective recall of age at onset of OCD may not reliable and complicate the precise time, in particularly adult patients. Prospective studies on the relationship of stable autistic and schizotypal traits and OCD soon after onset of the disorder may be more confidential. The type and severity of OCS may also differ based on the developmental stage of adolescent or adult patients. Furthermore, young children may not adequately report their symptoms.
The present study demonstrates the the higher association of stable autistic traits with the rate of obsessions among AO-OCD patients compared to adolescent subjects. Therefore, we can conclude that autistic traits may play a significant role in the occurence of OCS also in later ages. In further studies, the higher rates of autistic traits in adult-onset OCD patients should be explored considering the influences of genetic factors.
In the present study, the greater number of compulsions, a different OC symptom profile, and higher severity of autistic-like traits in AO-OCD patients may indicate that adolescent and adult-onset OCD have different clinical characteristics. Autistic traits seemed to be higher and had a closer relationship with the frequency of lifetime obsessions in AO-OCD patients than in adolescent patients. Higher rates of autistic traits in adult-onset patients may also reflect an important developmental distinction between the obsession and compulsion components of an OCD diagnosis.

Declaration of conflicting interests: the authors declared no conflicts of interest with respect to the research, authorship, and/or publication of this article. Funding The authors received no financial support for the research, authorship, and/or publication of this article.
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