9.1.1 Is autism an obsessive–compulsive spectrum disorder?
Beside the implications for treatment interventions outlined in the Introduction, another interesting aspect of studying the relationship between ASD symptoms and OCD is the ongoing debate about the nosological placement of OCD. Some researchers have suggested including OCD together with ASD, tic disorders, hypochondriasis, body dysmorphic disorder and trichotillomania as one part of the so-called obsessive–compulsive spectrum disorders (OCSD) (Bartz & Hollander, 2006; Hollander et al., 2007). The reasons for this unification are fourfold: the OCSDs share a core feature of repetitive thoughts and behaviour; the presence of phenotypic similarities such as age of onset, comorbidity, and family loading; the sharing of brain circuitry abnormalities, familial and genetic factors, and neurotransmitter
abnormalities; and the disorders may be treated pharmacologically with similar drugs. Others have strongly questioned this approach. Storch and co-workers (2008) argued forcibly that the symptoms of these disorders have different cognitive, motivational and
functional underpinnings. The functional role of compulsions was specifically pointed out as being different from that of behaviours in the other OCS disorders. Consequently, they argued, the OCSD construct is misleading.
One aspect of the OCD–ASD overlap is the elevated level of ASD comorbidity in OCD, which several researchers have reported in adults as well as in paediatric samples (Ivarsson & Melin, 2008; Ivarsson et al., 2008) (see section 5.3.1). Correspondingly, when appropriately assessed, OCD comorbidity is high in autistic samples (Leyfer et al., 2006; Russell et al., 2005). Another reason for the hypothesis of an OCSD was the phenomenological overlap between OCD, ASD and tics/TS (Hollander et al., 2007). The presence of, for example, repetitive behaviour in these disorders would be a common underlying feature. In ASD, repetitive behaviour is one of three defining symptom clusters, often meeting the need for sameness. In OCD, repetitive rituals are likewise present in most patients. However, as Storch and colleagues (2008) pointed out, repetitive behaviour in OCD has a different function, namely that of regulating anxiety. In a similar manner, Baron-Cohen (1989) suggested that the terms obsession and compulsion should be used with caution to describe autistic behaviours because they may fail to satisfy the definitions of OCD with regard to the ego-dystonic aspects (unwantedness, distress, resistance, senselessness), and recommended using the more descriptive term ‘repetitive activities’ instead. However, many patients with OCD have compulsions concerning ordering and symmetry, as well as repetition, in order to satisfy the need for a ‘just right’ feeling (Livingston-Van Noppen, Rasmussen, Eisen, & McCartney, 1990; Rapoport, 1989), which could be difficult to differentiate. Repetitive behaviour is the autistic symptom that is closest to the proposed core feature of the OCSD
(Hollander et al., 2007). Thus, if the theory of repetitiveness as a core feature of ASD holds, repetitiveness should be present during the preschool years at the onset of ASD symptoms, as well as in later childhood following the onset of OCD symptoms, which is usually at around 9–10 years of age (Masi et al., 2005). In addition, one would expect substantial continuity between ASD symptoms at preschool age and later in childhood and adolescence across all patients. To explore whether this is the case, we assessed ASD symptoms in children with OCD using a dimensional approach, covering both current and preschool ASD symptoms, compared with the general population. The comparison group was used to control for the presence of ASD symptoms in children and adolescents in general and for overall psychiatric symptoms in both groups.
Our results (study 1) showed that autistic symptoms were indeed more common in children with OCD than in the general population. Even if autistic symptoms that could be confused with OCD symptoms or tic-like symptoms were excluded, ASD symptoms occurred at a greater prevalence than in controls. However, in the sample as a whole, ASD symptom prevalence was low. The vast majority of OCD patients did not have these traits. Thus, the presence of ASD symptoms in paediatric OCD seems to indicate that ASD and OCD co-occur in a subgroup of cases rather than in OCD as a whole. In addition, those with autistic traits, who made up approximately a fifth of the OCD group, tended to have symptoms concerning communication difficulties more often than social difficulties in their preschool years. The most autism-specific symptoms (i.e., gaze avoidance, absence of social smile, and lack of shared attention, reciprocal social interaction and interest in peers) were not endorsed either. Thus, it would be difficult to construct evidence of a strong continuity between early
ASD traits in children who later develop OCD from the preschool symptoms alone. Moreover, only a few cases had high levels of preschool ASD symptoms. Contrary to the current symptom subscale of the SCQ (see Appendix 2), the preschool subscale does not include items related to repetitive/stereotyped behaviour. Therefore, repetitiveness might have been overlooked and missed in some cases. The current symptoms subscale generates a different problem, as several items overlap with both OCD (verbal rituals, compulsions and rituals) and comorbid tic disorder (hand and finger mannerisms and complex body
movements). For example, is the SCQ question on compulsions and rituals worded in such a way that OCD compulsions could be included, namely ‘‘Does she/he ever have things that she/he seems to have to do in a very peculiar way or order or rituals that she/he insists that you go through?” Similarly, tics might be confounded with the SCQ question ‘‘odd ways of moving his/her hands or fingers’’. In general, the association between preschool and current ASD symptoms was weak. Only the OCD subgroup with the highest level of preschool ASD symptoms demonstrated substantial continuity with current ASD symptoms.
The argument by Hollander (2007) and Bartz (2006) that OCD as a whole should be reclassified together with ASDs, tics/TS and various other disorders into an obsessive– compulsive spectrum group seems out of proportion, and was not supported by the level or type of current comorbid ASD symptoms, nor by the presence of preschool ASD symptoms in our study. However, the higher level of ASD symptoms in our OCD patients compared with controls, which existed independently of other psychiatric problems, might indicate that there is an underlying relationship in a subgroup of OCD patients.