|They say you're judged by the strength of your enemies.|
As per that link to previous work by Unenge Hallerbäck among others, the idea that the autism spectrum and the schizophrenia spectrum might not be as separate and independent as is commonly thought is gaining some renewed research momentum in recent times (see here). I wouldn't necessarily call it a reunification, as per older sentiments of autism being akin to childhood schizophrenia despite the fact that some of the criteria produced for example, by Mildred Creak and colleagues, contain some potentially pertinent information (see her 9 key features of ‘schizophrenic syndrome in childhood’).
Rather however a realisation that (a) autism is nothing like protective against the subsequent development of schizophrenia or related diagnoses particularly with a changing symptom profile moving into adulthood, and (b) in these days of RDoC (see here), common genetic / epigenetic / biological / behavioural ground may be evident across some cases of autism and some cases of schizophrenia including something of familial element . The fact that Prof. Gillberg also makes an appearance on the Lugnegård paper adds to the ESSENCE of overlapping comorbidity (see here) or autism plus  if you so wish.
Back to the recent Lugnegård study, and based on quite a bit of work in this area by the authors (see here), they aimed to: "examine the AS-schizophrenia discriminating ability of the AQ." The AQ for those that might not know, represents a series of questions/statements scored on the basis of the presence (or not) of specific cognitive-behavioural traits noted as part of the autism spectrum. It's been talked about a few times on this blog in relation to looking at sensory issues in autism (see here) and rather more uncomfortably, suicide ideation/attempts with parts of the autism spectrum in mind (see here).
The AQ "was completed by 136 individuals: 36 with schizophrenic psychosis, 51 with AS and 49 non-clinical comparison cases." The results: well, as a group, those with AS did score significantly higher than the schizophrenia group, who scored higher than the asymptomatic control group. That being said, there was quite a bit of overlap in the range of AQ scores obtained across the groups and particularly when it came to those with AS and those with schizophrenia. Ergo, using one of the more popular self-report measures for autism, some on the schizophrenia spectrum might also present with a prominent level of autistic traits as part of their symptom profile.
Obviously one has to be slightly cautious with such findings. Self-report is subject to quite a few forms of bias; to some degree complicated by the questions and grading system used by the AQ (take the test here if you wish) which is very subjective in itself (e.g. " I prefer to do things with others rather than on my own" - in what context... going for a drink, taking a bath, etc.). That being said, papers such as the one by Shaun Eack and colleagues  (open-access) reporting "considerable similarity in social and non-social cognitive impairment in verbal adults with ASD and outpatients with schizophrenia" under more controlled conditions, offer something of a complementary viewpoint to the Lugnegård and other findings. And before you ask, such overlap in presentation might not just be accounted for by other comorbidity either .
Appreciating that diagnostic identity is still an important part of both autism and schizophrenia spectrums for all-manner of different reasons, the idea of compartmentalising when it comes to diagnostic labels is seemingly on less secure ground that it has been for many years. Fuzzy diagnostic boundaries intra-diagnosis - y'know the heterogeneity of the spectrums - has been further complicated by fuzzy diagnostic boundaries inter-diagnosis. And things are only likely going to get even more complicated as per the paper by Song and colleagues  for example...
And now for some music... Duck Sauce - Barbra Streisand
 Lugnegård T. et al. Asperger syndrome and schizophrenia: Overlap of self-reported autistic traits using the Autism-spectrum Quotient (AQ). Nord J Psychiatry. 2014 Nov 12:1-7.
 Sullivan PF. et al. Family History of Schizophrenia and Bipolar Disorder as Risk Factors for Autism. Arch Gen Psychiatry. 2012;69(11):1099-1103.
 Gillberg C. & Fernell E. Autism plus versus autism pure. J Autism Dev Disord. 2014 Dec;44(12):3274-6.
 Eack SM. et al. Commonalities in social and non-social cognitive impairments in adults with autism spectrum disorder and schizophrenia. Schizophr Res. 2013 Aug;148(1-3):24-8.
 Mealey A. et al. Overlap between autistic and schizotypal personality traits is not accounted for by anxiety and depression. Psychiatry Res. 2014 Oct 30;219(2):380-5.
 Song DK. et al. Comparative analysis of autistic traits and behavioral disorders in Prader-Willi syndrome and Asperger disorder. Am J Med Genet A. 2014 Nov 11.
Lugnegård T, Hallerbäck MU, & Gillberg C (2014). Asperger syndrome and schizophrenia: Overlap of self-reported autistic traits using the Autism-spectrum Quotient (AQ). Nordic journal of psychiatry, 1-7 PMID: 25389915