A supplement finds a niche in chronic depression and older adults
STUDY: Kumar R et al, Neuropsychiatric Disease and Treatment 2026
STUDY TYPE: Systematic review and meta-analysis
FUNDING: National Institutes of Health (NIH), National Center for Advancing Translational Sciences (NCATS), Mayo Clinic, National Network of Depression Centers, Breakthrough Discoveries for Thriving with Bipolar Disorder
Background
Patients with major depressive disorder have lower blood levels of acetyl-L-carnitine (ALC) than healthy controls, and levels are particularly low in depressions that are severe, chronic, or associated with childhood trauma. ALC is natural and helps mitochondria burn fatty acids; it aids neuroplasticity through BDNF, glutamate signaling, and epigenetic pathways.
The Study
- 15 trials (14 randomized controlled trials, 1 open-label) with 809 participants, ages 18 to 93.
- 10 trials with sufficient data entered the meta-analysis (366 ALC, 359 control).
- Comparators varied: ALC vs. placebo, ALC vs. active antidepressant (amisulpride, fluoxetine), and ALC added to an antidepressant vs. the same antidepressant alone.
- ALC doses ranged from 1 to 3 g/day; trial duration ranged from 40 days to 12 weeks.
- Most trials enrolled older adults with major depressive disorder or dysthymia; one trial focused on bipolar depression.
Results
Across 10 randomized controlled trials, ALC outperformed control on depression rating scales (Hedges’ g = −1.20, 95% CI −2.12 to −0.29). The effect was consistent across sensitivity analyses, including when the one high-risk-of-bias trial was dropped.
The clearest signal came from trials where ALC was given alone versus placebo (Hedges’ g = −2.41). Head-to-head comparisons against active antidepressants showed roughly similar results between groups, with no clear superiority in either direction.
ALC worked better in older adults (age ≥60) than in younger patients. The subgroup difference was statistically significant (p = 0.03), with an effect size nearly seven times larger in the older group (Hedges’ g = −1.88 vs. −0.28).
Neither dose nor duration predicted response in meta-regression, though the analysis was underpowered.
ALC showed no benefit in bipolar depression in the one trial that tested it.
Side Effects
ALC is safe with side effects in these trials limited to GI complaints.
Limitations
- High heterogeneity across trials (I² = 97%), reflecting differences in populations, doses, and comparison groups.
- Most studies were small and conducted in Italy; possible publication bias detected.
Practice Implications
- Consider ALC for depressions in older adults, chronic dysthymic moods, and patients with a history of childhood trauma. It also has trials in comorbid medical disorders.
- This is one supplement I have seen responses with.
- Target dose 1 to 3 g/day, typically divided into two or three daily doses. Start with 1 gram/day and raise every week. Find reliable products here.
—Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report
