Accuracy of Autism Self-Diagnosis
But that gave me an idea, and I found another Wrong Planet thread, a stickied thread where a poster had linked to several online tests useful for self-assessment of autistic traits. Overall, 237 people (myself included) had posted their results on at least one of these tests, including 63 diagnosed with Asperger Syndrome, 20 with other autism spectrum conditions, 76 self-diagnosed Aspies, 65 who were unsure if they were on the spectrum or not, 11 with a family member on the spectrum and 2 neurotypicals. (The latter two groups were put together for further analysis.) There were 101 males and 136 females, similar to the gender ratio in my previous study. All the groups had similar gender ratios.
The tests taken were the Broad Autism Phenotype Questionnaire, the Autism Spectrum Quotient, the Empathizing and Systemizing Quotients, the Emotional IQ Test, the Highly Sensitive Person test, the 'Reading the mind in the eyes' test, the Cambridge Face Memory test (the link is broken), the Aspie Quiz, the Asperger Syndrome Self-Assessment test and the Toronto Alexithymia Scale. Of those 10 tests, 5 directly assess for autistic traits, 2 test for social skills but not other aspects of autism, and the last 3 assess conditions that commonly co-occur with autism.
A one-way ANOVA found significant differences between groups on the BAPQ aloof and pragmatic scales, ASQ, EQ and Aspie Quiz. In all of those cases, this difference was due to the family/NT group scoring as less autistic than the other groups. In most cases, all four autistic/possibly autistic groups scored significantly more autistic than the family/NT group, with the exception of the BAPQ pragmatic scale in which only the diagnosed Asperger Syndrome and the self-diagnosed group's differences reached significance (these groups also have the largest sample size). None of the other four groups showed any significant differences with each other.
Then I decided to see which percentage of individuals in each group met cutoff scores on the various tests.
The BAPQ is designed to assess the broader autistic phenotype, rather than autism spectrum conditions. As a result, the cutoff scores (89 for aloof, 81 for rigid and 79 for pragmatic) simply determine whether or not the person has a genetic predisposition to autism, and not whether they're autistic. However, autistic people would be expected to score quite high on this scale, and so they do (group differences almost significant at p=.073):
- diagnosed AS: 87% meet cutoff on all three scales, 4% on 2 scales and 9% on one scale only
- other autistic: 89% meet cutoff on all three scales and 11% on only 2 scales
- self-diagnosed: 91% meet cutoff on all three scales, 4% on 2 scales and 1% on one scale only
- unsure if autistic: 88% meet cutoff on all three scales, 10% on 2 scales and 2% on one scale
- family/NT: 67% meet criteria on all three scales and 33% meet criteria on none of the scales (sample size of 3)
- diagnosed AS: 92% scored at or above 32
- other autistic: 69% scored at or above 32
- self-diagnosed: 95% scored at or above 32
- unsure if autistic: 83% scored at or above 32
- family/NT: 43% scored at or above 32
- diagnosed AS: 90% Extreme S, 3% S, 5% Balanced and 2% E
- other autistic: 81% Extreme S, 13% S and 6% Balanced
- self-diagnosed: 96% Extreme S, 4% S
- unsure if autistic: 92% Extreme S, 6% S and 2% Balanced
- family/NT: 50% Extreme S and 50% Extreme E (sample size of 4)
The Asperger Syndrome Self-Assessment had very low response rates, with 3 diagnosed AS, 1 other autistic, 1 self-diagnosed and 3 unsure if autistic participants filling it out. As a result, I will not analyze it further.
The Highly Sensitive Person test assesses a personality construct of high reactivity to physical and emotional stimuli. The stereotypical highly-sensitive person is highly empathetic and therefore not autistic, but the test taps many questions regarding sensory sensitivities and therefore autistic people are expected to score highly. The Cambridge Face Memory test assesses for prosopagnosia, an impairment in facial recognition. Prosopagnosia appears to be a common comorbid condition for autism. The Toronto Alexithymia Scale assesses alexithymia, an impairment in understanding one's own emotions (in contrast to the autistic impairment in understanding other people's emotions). Alexithymia is more common in autism spectrum individuals than the general population. However, only 5 respondents filled out the TAS, so I excluded it from further analysis. I assessed presence of the other two conditions, using a cutoff of 14 or above for the HSP test and less than 55% correct for the CFMT (differences between groups non-significant at p=.429 for HSP and p=.121 for prosopagnosia):
- diagnosed AS: 94% highly sensitive, 22% prosopagnosic
- other autistic: 93% highly sensitive, 30% prosopagnosic
- self-diagnosed: 83% highly sensitive, 9% prosopagnosic
- unsure if autistic: 85% highly sensitive, 6% prosopagnosic
- family/NT: 67% highly sensitive, none prosopagnosic (sample size 3 for both)
- diagnosed AS: 84% scored 3, 8% scored 2, 4% scored 1 and 4% scored 0
- other autistic: 67% scored 3, 8% scored 2 and 25% scored 1
- self-diagnosed: 88% scored 3, 9% scored 2 and 3% scored 1
- unsure if autistic: 70% scored 3, 23% scored 2 and 7% scored 1
- family/NT: 50% scored 3 and 50% scored 0 (sample size 6)
Oddly enough, though, most of the participants, even those with official diagnoses, scored in the normal range or better on this test (22 or more correct), with 47% of diagnosed AS, 39% of other autistic, 28% of self-diagnosed, 32% of unsure and none (out of 2) of the family/NT group scoring in the deficient range. The average scores (22.03, 21.23, 23.65, 23.05 in the four autistic groups) are similar to the findings of Baron-Cohen et al (2001), and suggest that many high functioning autistics have too subtle of deficits for this test to detect. One possible alteration could be to make this test timed, as many autistic participants reported that this test took a long time to complete. (Also, a few reported giving up on the test because they had no clue about any of them, suggesting that some of the most severely-impaired participants may have been omitted from the test's analysis.) Another possibility might be to make it free response instead of multiple choice, since some participants said that what they thought was the correct answer was not even one of the options.
Ideally, I would like to run a study in which a large sample of self-diagnosed autistics were assessed by a team of psychologists experienced in diagnosing adult high-functioning autistics. However, this study suggests that self-diagnosed autistics - at least those on the Wrong Planet forum - score about the same as officially diagnosed autistics on a wide variety of tests. Contrary to the stereotype that self-diagnosis of autism is inaccurate, this study suggests that it's actually very accurate in the majority of cases. Undoubtedly some self-diagnosed autistics are not in fact on the autism spectrum, but so are some officially diagnosed autistics. And from what I can tell, the misdiagnosis rate is pretty similar between self-diagnosis and official diagnosis.