Effect Sizes for Stimulants and ECT in ADHD and Depression
Stimulants for ADHD
Stimulant medications demonstrate a robust effect size of 1.0 for treating ADHD symptoms, representing the gold standard pharmacotherapy with the strongest evidence base. 1
Effect Size Data by Medication Class
- Methylphenidate and dextroamphetamine: Effect sizes range from 0.8 to 1.0 SD on teacher-rated behavioral measures in short-term trials 1
- All stimulant classes (methylphenidate, dextroamphetamine, mixed amphetamine salts): Demonstrate equivalent efficacy with effect size of approximately 1.0 1
- Nonstimulant medications (atomoxetine, extended-release guanfacine, extended-release clonidine): Lower effect size of 0.7 1, 2
Clinical Context of Stimulant Effect Sizes
- The effect size of 1.0 translates to a 70-80% response rate when a single stimulant is tried in controlled studies involving over 5,000 school-age children 1, 3
- Individual response varies significantly: approximately 40% of patients respond to both methylphenidate and amphetamine, while 40% respond to only one class 1
- Effect sizes remain consistent across age groups, with adult studies showing similar magnitude of benefit as pediatric trials 4
Comparative Efficacy by Stimulant Type
Long-acting versus short-acting stimulants: Meta-analysis found no significant differences in effect sizes between formulations, though long-acting preparations offer practical advantages for adherence 4
Dose-response relationships:
- Fixed-dose trials show increased efficacy with higher doses, but incremental benefits plateau beyond 30 mg methylphenidate-equivalent or 20 mg amphetamine-equivalent 5
- Flexible-dose trials demonstrate continued efficacy improvements across the FDA-licensed dose range because practitioners can titrate based on symptom control and tolerability 5
Important Caveats
- Effect sizes are derived primarily from short-term trials (mean duration 5.3 weeks), with only 22 of over 160 controlled studies lasting more than 3 months 1
- Fewer than half of children show complete normalization of symptoms despite the large effect size 1
- Stimulant effects on behavior are not specific to ADHD and occur in individuals with other disorders and normal subjects 1
ECT for Depression
The provided evidence does not contain any data on ECT effect sizes for depression or any other condition. The guidelines and research focus exclusively on ADHD pharmacotherapy, with no mention of electroconvulsive therapy.
What the Evidence Does Address
The guidelines discuss depression treatment in the context of ADHD comorbidity:
- When major depressive disorder is primary or severe (with psychosis, suicidality, or severe neurovegetative signs), depression should be the initial treatment focus 1
- For less severe comorbid depression, stimulants may be tried first as ADHD symptom reduction can improve depressive symptoms 1, 3
- SSRIs can be safely added to stimulants if depressive symptoms persist after ADHD improvement 3
Clinical Algorithm for Comorbid ADHD and Depression
- Assess depression severity: If MDD is primary with severe symptoms, treat depression first 1
- For moderate depression with ADHD: Initiate stimulant trial first, as rapid onset (days) allows quick assessment of ADHD response 1, 3
- Reassess after stimulant response: If ADHD improves but depression persists, add SSRI to stimulant regimen 3
- Avoid MAO inhibitors: Never combine with stimulants or bupropion due to hypertensive crisis risk 3
Summary of Available Effect Size Data
| Intervention | Effect Size | Quality of Evidence |
|---|---|---|
| Stimulants (ADHD) | 0.8-1.0 | High (160+ RCTs) [1] |
| Nonstimulants (ADHD) | 0.7 | Moderate [1,2] |
| ECT (any indication) | No data available | N/A |
The evidence strongly supports stimulants as first-line treatment for ADHD with the largest effect sizes documented in psychiatry, but provides no information regarding ECT efficacy or effect sizes.