Reasons to pause when discussing a "sensory processing disorder" construct.
The Sensory Profile is an assessment tool that purports to measure sensory processing abilities (Pearson Education Inc., 2008); there are versions for infant/toddlers, school aged children, and adolescent/adult populations. The tool has been used to document the incidence of a "sensory processing disorder" construct (Ahn, et. al., 2004; Ben-Sasson, et. al., 2009). To date, although many scientists recognize that children can have difficulties with processing sensory information, this diagnostic construct has been rejected and is not considered as a distinct clinical entity (AAP, 2012). For more in depth reading, please reference previous blog posts here.
I was interested to see an article in a recent OT Practice magazine regarding sensory processing abilities of children involved in the justice system (Shea and Wu, 2013). The article presents an interesting test case for use of the Sensory Profile to help understand the nature of some difficulties that these adolescents may have.
Face validity is a construct that relates to whether or not an assessment measures what it is supposed to measure. The question we can ask about this study is: Does the Sensory Profile measure what it is supposed to measure? A statement in the article that caught my attention was
The occupational therapists were particularly surprised by the low score in sensation seeking, because they had hypothesized that these youths would have higher sensation-seeking tendencies, and their need to seek sensory stimulation may have led them to delinquent behaviors...The combination of high-sensation-avoiding and low-sensation-seeking profiles implies that the youth participants would be less likely to seek sensory stimuli and more likely to avoid stimuli than we had expected.
I had a similar experience with the Adolescent Adult Sensory Profile as documented here. In my doctoral study, I hypothesized that people with Complex Regional Pain Syndrome would have heightened scores on Sensory Sensitivity scales. Just as the authors in the present study, I was surprised that Sensory Profile Scores were quite different from what I expected.
Still, in both instances, the scores were atypical - they were just atypical in directions other than what was hypothesized. This leads to a concern that I have with face validity of the tool. It is certainly measuring something, but is it measuring sensory processing? Is it measuring it the way that we think it is measuring things? When a tool ends up giving us information that is diametrically opposed to what we believe we are going to get out of it then I think we need to start asking some serious questions about what it is exactly that we are measuring, and whether or not our theoretical construct and understanding is correct.
Other questions seem rather pertinent:
1. Do the high numbers of atypical scores really indicate that 40-45% of this juvenile justice population has a 'disorder.' That level of identification, if sensory processing difficulties as measured really are a disorder, would be rather stunning.
2. Do people who have atypical scores on the Sensory Profile truly represent a subset of the population that could also be more prone to violence or asocial behavior? The Sensory Processing Disorder Foundation was quick to jump on the Sandy Hook massacre and describe Adam Lanza's behavior as a sensory 'diagnosis,' much to the outrage of families who made their opinions on the matter quite clear on the SPD website.
3. A fact not mentioned in the article is that in the past a small study was done on sensory profiles of people who have mental illness, and the distribution of scores as described for people who have schizophrenia was identical to the pattern of scores reported in this study - low sensory seeking and high sensory avoiding (Brown, et.al., 2002). Other scientists have more recently supported the notion that the population of people who have schizophrenia also have sensory processing difficulties (Javitt, 2009). It has been widely quoted that the incidence of mental health diagnoses in the justice system is 16% (Ditton, 1999). Since so many people in the current study scored atypically, is the Sensory Profile just measuring a "sensory processing disorder" construct, or is it measuring something else?
This analysis should help us to more deeply understand that our current assessment tools, which are apparently measuring something, may not just be measuring a sensory processing construct. In my opinion, the assessment tool also includes many questions that are broad and general and could represent a number of behavioral phenomenon, primarily dependent on the interpretation or labeling of the examiner.
I believe that we should consider pausing when we use tools like the Sensory Profile to report an incidence of "sensory processing disorder." It is apparent that atypical scores on this assessment may indicate co-morbid issues that are interwoven with a number of other behavioral and social and psychiatric diagnostic constructs.
Ahn, R. R., Miller, L. J., Milberger, S., and McIntosh, D. N. (2004). Prevalence of parents’ perceptions of sensory processing disorders among kindergarten children. American Journal of Occupational Therapy, 58, 287–293
American Academy of Pediatrics (2012). Policy Statement: Sensory Integration Therapies for Children With Developmental and Behavioral Disorders. Pediatrics, 129(6), 1186-1189.
Ben-Sasson, A., Carter, A.S., and Briggs Gowan, M.J. (2009). Sensory over-responsivity in elementary school: prevalence and social-emotional correlates. Journal of Abnormal Child Psychology, 37, 705-716.
Brown, C., Cromwell, R., Filion, D., Dunn, W., and Tollefson, N. (2002). Sensory processing in schizophrenia: missing and avoiding information. Schizophrenia Research, 55(1-2):187-95.
Ditton, P.M. (1999). Mental Health Treatment of Inmates and Probationers, Washington, DC: US Department of Justice, Office of Justice Programs, Bureau of Justice Statistics.
Javitt, D.C. (2009). Sensory processing in schizophrenia: Neither simple nor intact. Schizophrenia Bulletin, 35(6), 1059-1064.
Pearson Education, Inc. (2008). The Sensory Profile Technical Report. Retrieved 10/29/13 from http://www.pearsonassessments.com/NR/rdonlyres/6AB47882-1271-4D6A-BB3D-1AF8692D67B9/0/SP_TR_Web.pdf
Shea, C. and Wu, R. (2013). Finding the Key: Sensory Profiles of Youths Involved in the Justice System. OT Practice 18(18), 9–13.