Sluggish cognitive tempo: the need for global inquiry

Abstract

The construct of "sluggish cognitive tempo" (SCT), a set of symptoms characterized by excessive daydreaming, mental confusion and fogginess, drowsiness, and slowed thinking and behavior, was introduced over three decades ago. Despite a recent increase in research attention, SCT remains largely unfamiliar to researchers and clinicians alike. Moreover, SCT has been primarily examined in the US, with only a handful of studies from Western Europe and even fewer from other parts of the world. Here I provide a brief summary of key SCT findings and draw attention to the need for greater worldwide investigation of this construct, including its phenomenology, etiology and course, concomitants and developmental consequences, and clinical implications. The study of SCT has been closely tied to that of attention-deficit/hyperactivity disorder (ADHD), and this historical association remains present in much of the literature. SCT is strongly associated with ADHD inattentive symptoms, though meta-analytic findings also support their differentiation1. Another consistent finding is the separation of SCT and ADHD inattention in their relations with other psychopathologies: SCT is strongly associated with internalizing symptoms, especially depressive symptoms, yet unassociated or negatively associated with externalizing behaviors when controlling for ADHD inattention; conversely, ADHD inattention is consistently associated with externalizing behaviors and less clearly associated with internalizing symptoms when controlling for SCT1, 2. Consistent with SCT's association with internalizing symptoms, there is emerging evidence of an association between SCT and suicide risk3, and SCT symptoms are also associated with social difficulties, particularly social withdrawal and isolation1, 2. Findings for academic functioning and neurocognition are somewhat mixed, though there is initial evidence for SCT being associated with greater academic impairment, lower academic achievement scores, slower processing speed, and poorer sustained attention1, 2. Finally, SCT predicts non-response or poorer response to methylphenidate among children with ADHD4, underscoring the clinical relevance of this constellation of symptoms. Still, the study of SCT remains in its infancy, with a number of findings yet to be replicated and other areas of inquiry untouched entirely. This is an opportune time for a worldwide study of SCT. A recent meta-analysis identified SCT symptoms that are empirically distinguishable from ADHD inattentive symptoms1, and subsequent measurement work has validated SCT rating scales, with a consistent symptom set that can be used across parent, teacher, child and adult informants. Several translations of these measures are starting to emerge or are currently in progress. It has become clear that the wording of some SCT items may be culture-bound idioms in the English language that are not readily subject to translation (e.g., "mind gets mixed up", "seems to be in a fog"). A standard symptom set that can be readily translated into various languages is an important first step to the global inquiry of SCT. As validated measures become available, they can be used to examine whether SCT symptoms are similarly identifiable across and within cultures. This is necessary to establish the transcultural validity of SCT and better understand its phenomenology, development, and functional impact. It is possible that SCT is more prevalent or harmful in certain contexts. For example, SCT-related shyness and withdrawal may be more detrimental for broader social functioning in some cultural contexts compared to others5. At the same time, it should be considered whether the presence of SCT and its impact on functional outcomes is attributable to, or exacerbated by, societal factors, in ways that echo findings linking variation in ADHD diagnosis rates to educational accountability policies in the US6. The worldwide study of SCT would also allow for investigations of global factors such as solar intensity that have been associated with variation in ADHD prevalence rates7. There may also be different cultural attributions for SCT behaviors (e.g., daydreaming), that could in turn have important implications for what prevention and intervention efforts would be perceived as acceptable. These types of intriguing questions can only be addressed if SCT arises to a level of global inquiry. Finally, it has already been suggested that SCT may be a new psychiatric condition identified, in part, to provide more opportunities for psychotropic intervention8. Establishing the global prevalence and impact of SCT would help alleviate concerns that the SCT construct is garnering empirical validation not for the clinical needs of patients but for the profits of pharmaceutical companies. It took over 40 years before a seminal review published in this journal asked whether ADHD was an American condition9. It would be prudent to learn from the history of ADHD and to exam