Psychiatry Research Review

Lisdexamfetamine in the Treatment of Comorbid Sluggish Cognitive Tempo and Adult ADHD: Placebo-controlled Trial

Adler LA, et al. J Clin Psychiatry. 2021;82:20m13687.

Background
Sluggish cognitive tempo (SCT) is a cluster of symptoms associated with attention difficulties and is common in attention-deficit/hyperactivity disorder (ADHD). Patients with SCT may have difficulty concentrating and staying alert, feel lethargic frequently, and get confused easily or struggle to process information quickly and accurately. SCT was previously shown to add to the impairment seen in ADHD, but the effect of stimulant medication on SCT symptoms was unknown. This study examined the efficacy of the stimulant lisdexamfetamine (LDX) vs a placebo on SCT symptoms and executive functioning attributes in adults with comorbid ADHD and SCT.

Methods
Thirty-eight patients with DSM-5 ADHD and SCT were recruited from 2 academic medical centers and randomized to receive 4 weeks of LDX 30-70 mg/day or placebo before a 2-week washout period and crossover to the other arm for an additional 4 weeks. The Barkley Adult ADHD Rating Scale-IV SCT subscale and the ADHD Rating Scale were used to measure patient outcomes.

Results
LDX improved SCT score ratings compared with placebo on SCT ratings in both treatment periods, but this reached significance only in the first 4-week treatment period (prior to crossover). Patients who received LDX had significantly improved ADHD symptoms, executive functioning, and ratings of functional impairment compared with patients who received the placebo. No interactions were observed between sex, age, race, and ethnicity and the outcome measures.

Conclusions
LDX significantly improved ratings of SCT, ADHD, executive functioning, and impairment in adults with comorbid ADHD and SCT.

Clinical Commentary
SCT when present with ADHD adds to the impairment and leads to difficulty in treatment. This was a randomized clinical trial with placebo comparison that used standardized rating scales and careful diagnosis to characterize the study population. There were not enough patients to examine whether patients with different ADHD subtypes responded differently to LDX.

Clinical Insights

• This is the first study to find the effects of stimulants on SCT in adults with comorbid ADHD and SCT.

• Healthcare professional should screen for symptoms of SCT in adult ADHD patients and treat with stimulants such as LDX.
• Adverse events were consistent with what was previously known and included trouble sleeping or falling asleep, dry mouth, and anxiety. There were no reports of emergent suicidal ideation.

Summary
As a healthcare professional, I have observed symptoms of SCT in my patients but must admit I only heard the terminology of “sluggish cognitive tempo” when I read this study. Healthcare professionals should screen adult patients with ADHD for SCT, and if SCT is observed, an adequate trial of LDX should be done (maximum dose of 70 mg/day for 4 weeks).