Response on Eme, R. (2011) Sluggish cognitive tempo
By Robert Eme
Dr. Buckhalt proposed that SCT symptoms may be due to a sleep disorder and when such symptoms are manifest they warrant a referral for a sleep disorder. Of course, such symptoms may be due to a sleep disorder, or other disorders. Hence, in essence, this raises the issue of differential diagnosis. A sleep disorder (or other disorders, e.g., PTSD) must be ruled out before SCT symptoms can be attributed to a primary attention disorder. However, the inference that the issue of differential diagnosis provides compelling evidence that SCT is either not a valid disorder or that SCT symptoms should routinely and preferentially prompt a referral for a sleep disorder evaluation does not correspond with the research as per the following three points:
First, in asserting that the most obvious explanation for SCT symptoms is a sleep disorder, two points that were made in my original article have been overlooked. First, the article discussed the crucial finding that the SCT symptoms of drowsy and daydreams are more diagnostic of attention problems than all but one of the symptoms that are currently included in the official DSM list. Thus, there is robust evidence from the research done in establishing the criteria for attention problems in the DSM-IV that SCT symptoms are strongly indicative of an attention problem, not a sleep disorder. Hence, if such symptoms are present, the first diagnostic consideration should be SCT rather than a referral for a sleep disorder evaluation.
Second, since there is incontestable scientific evidence for an 'alerting' attentional network (Posner & Rothbart, 2007), this leads to the obvious conclusion that there should be a SCT syndrome since there is an 'alerting' attentional network whose impairment can result in impaired 'alertness.' This conclusion receives overwhelming support from the literature on the most common form of severe traumatic brain injury (closed head injury) which typically results in a sequela of 'slow processing speed' (aka 'sluggish' processing speed) since such an injury typically impacts multiple neuronal networks, including the 'alerting'attentional network (Allister, 2008; Yeates, 2010). This sequela is obviously not primarily due to a sleep disorder, though the medical problems associated with traumatic brain injury, which can doubtlessly affect sleep, may also be a factors. Thus an impairment of the 'alerting' attentional network does indeed result in SCT symptoms. Second, adults with SCT symptoms commonly report feeling 'sluggish' despite having no sleep problems (Brown, 2006). Hence it is quite clear that SCT can be present in the absence of any obvious sleep disorder. If this evidence is countered with the gratuitous assertion that self-report may be inaccurate, what is gratuitously asserted can be gratuitously denied. In short, the extent self-report evidence supports SCT symptoms as indicative of an attention disorder, not a sleep disorder. Moreover, and since sleep problems are a common occurrence in ADHD (Barkley, 2006), it follows that an individual can be co-morbid for both SCT and sleep problems. Thus, the presence of a sleep disorder does not automatically rule out the presence of SCT and vice versa.
Third, case history evidence validates the efficacy of stimulant treatment for SCT (Solanto et al., 2009), although it may not be as effective as stimulant treatment for ADHD. Responsiveness of SCT symptoms to stimulant treatment supports SCT as an attention deficit disorder, not a sleep disorder.
In conclusion, the possibility that sleep disorders can result in SCT symptoms does not negate the considerable evidence that supports SCT as valid attention disorder. Thus, the need for differential diagnosis of SCT from a sleep disorder does not disqualify SCT as a valid disorder any more than the need for differential diagnosis for any of the 234 some disorders in the DSM disqualifies them as valid disorders. Furthermore, although an important implication of Dr. Buckhalt's commentary is the need to screen for and rule out a sleep disorder as a primary cause of SCT symptoms, the evidence suggests that a primary diagnostic option remains SCT with a rule out for a sleep disorder, rather than vice versa.
Barkley, R. (2006). Attention-deficit hyperactivity disorder (3rd ed.). New York: Guilford Press.
Brown, T. (2006). The unfocused mind in children and adults. New Haven, CT :Yale University Press.
McAllister, T. (2008). Neurobehavioral sequelae of traumatic brain injury: Evaluation and management. World Psychiatry, 7, 3-10.
Solanto, M., Newcorn, J., Vail, L., Gilbert, S., Ivanov, I., & Lara, R. (2009). Stimulant drug response in the predominantly inattentive and combined subtypes of Attention-Deficit Hyperactivity Disorder. Journal of Child and Adolescent Psychopharmacology, 19, 663-671.
Yeates, K. (2010). Traumatic brain injury. In K.Yeates, M. Ris, H. Taylor, & B. Pennington (Eds.), Pediatric neuropsychology: theory, research and practice (2nd ed., pp. 112-146). New York: Guilford Press.